Welcome to the forum.
Tires have a 5 year life. If the tires on the car are factory then they should be replaced. Take that into consideration.
You need to decide if the price is good.
KBB says a private sale of similar car should be about $8600
It depends on how good a friend he is. I would offer 9k and see how it goes. His asking price is a bit high in my opinion but not totally unreasonable.
A strategy would be to go to an internet dealer like Car Max and find a similar car and price it. Then decide. You could also use that price as a basis for negotiating with your friend.
The car sounds very nice. The rear defroster connector is probably repairable. the dealer can do it for you or you can buy a repair kit and do it yourself.
Here is a general checklist with some items to look for
1) Run a CARFAX report to check for any issues on record
2) Go to the GM dealer with the VIN and pull a report from the GM maintenance database, it will provide a lot of useful info on maintenance, failures, mileage, and recalls applied or outstanding
3) Early 08s had the electric vacuum brake booster pump deleted. Some have had issues due to this. There are two fixes, one software one adds the pump back to the car as a "kit"
4) 09s had the center double cup holder deleted. Many find this a problem and some have had the dealer install one. See threads on this subject
5) 2010 MY has updated engine management software and is not compatible with the GMPP tune.
6) Check the front cup holder to see if it’s there and functional.
7) Visually inspect the differential for seeping / leaking and operation. Some 07s had noise issues and there was a recall to install a special additive to address issues.
8) Visually inspect the undercarriage. Look for damage due to lifting in the area of the front fenders and the front lift points. Put a torque wrench on the bolts that retain the wheels on the inside as there are a few cases of these coming loose. Check the shocks for leakage, there are a few instances of them failing prematurely.
9) Visually inspect the "chin" for damage, many have been run into curbs and need repair. It’s a place where you can easily get it fixed but could negotiate the fix into the purchase price.
10) Cycle the tops several times for proper operation and look for any wear on the sides where the trunk hold down feet contact the fabric. Some scuffing is ok but the unwary owner has often had the top holed in this area. Visually inspect the trunk lid to make sure the rubber portion of the hold down feet are intact and properly aligned. Check the top for proper deployment and any sticking as well as general alignment. Make sure the twin flaps move freely and smoothly. Verify that both buttresses release easily and completely. Check the condition of the trunk hinges and the torsion bars. If the trunk has popped open when in motion, the hinges can be damaged and the torsion bars are known to fail occasionally. The fix is to pull the rear bumper cover and while it’s not difficult, it can be a significant labor charge to get it done.
11) Visually inspect the center console. Many have failed due to their design. If the previous owner put any significant weight on the center console cover, it is most likely cracked. The cracking starts at the curved rear portion on the driver’s side and progresses up through the center of the console cover. Often you can press down on the cover and see it flexing abnormally in this area and determine that it is unsound. It’s an easy fix, but if out of the bumper to bumper warranty, it will cost about $100 for a new part. If in doubt, pull up on the rear of the console cover and it will pop up so you can visually inspect the underside.
12) Visually inspect the tire pump assembly in the trunk. It’s about $50 to replace and its all you have on the road.
13) Visually inspect the intercooler for damage or defects. Many have been run into curbs and damaged, they are subject to foreign object damage on the road and unless you give them a good look you may not discover it until you have a problem. In rare instances, GMPP equipped GXPs have experienced splitting of the IC can on the outlet side. It is hidden by the plastic shroud but you can infer damage if there are codes thrown regularly or on cold start you listen up front near the ground you can hear a sucking sound.
14) Manually inspect the hose clamps for tightness. Give the air cleaner a quick look. If its full of tons of junk, that may be an indicator of the attention that the car received from the current owner and be a subject for triggering a more detailed inspection of the car by a trusted tech.
15) Check the condition of the MAF sensor where it mates with the intake tubing up front. Some have been broken off and glued back on as an expedient repair. This is not necessarily bad but is another indicator of the level of attention the current owner gave to the car.
16) Check for heavy uneven wear in the tires. If they were rotated as required, they should be evenly worn. If they are not, then that is another indicator.
17) Pull up the passenger side carpet and give the BCM a quick look. Is the cover in place? Does it show signs of having been removed frequently? Are there any signs of modification or tampering?
18) Inspect the fuse / relay box on the left side of the engine bay at the firewall. Look for any signs of problems, excessive handling or modifications.
19) Visually inspect the turbo for any signs of external cracking, oil leaking, or “modifications” to the actuation rod. The locktite should be intact with no signs of the nut having been turned.
20) Check the coolant level and color. If there is any question or anomaly, have it tested for specific gravity.
21) Have a person sit in the passenger seat to verify the proper operation of the seat airbag sensor. Several have failed and its relatively expensive to have them repaired out of warranty.
22) Check for proper operation of the driver’s seat lift motor. Many are never used and need to be lubricated to free them up properly.
23) Road test the car. Make sure all systems are functional. Check the DIC for all displays and the presence of any codes or warnings.
24) Visually inspect all the rubber seals – they are hard to find and some are very expensive.
25) Visually inspect the condition of the headlight and tail light assemblies. They are expensive and difficult to find. Some light pitting can be polished out but cracks are a problem.
26) For automatic cars, drive the car in low speed conditions an check for smooth upshifts and downshifts. Some cars are experiencing very hard 3-2 and 2-1 downshifts apparently due to undiagnosed camshaft position sensor failures.