I would have ALL fluids changed. Trans, diff, brake and coolant. I would check your belt....if it's cracked, replace it. I would also check your hoses...brake and coolant. But that's just all me as I'm anal.... It's also right around the time that most wheel bearings start to make noises.... If you drive it hard, check for play in these at each wheel.
Seltzinator just hit 100k towards the end of last year and I think he had the tranny and rearend fluid done at 70. the belts like ghost mentioned are a must and I'd flush the radiator if you haven'e done so as well as brake fluid like he also mentioned. and wheel bearings and see if you can reach up and check your body mount bushings. they can really make a car seem like it's riding rough and if those are worn, you can replace shocks and front suspension and it will still have a rough, rattling ride.
i dont see a drain to let the old coolant out ,is there one ? , and no cap to fill it , do you pull the top hose off and fill it with new coolant , dont see any other way , Thanks For the Help , New to the solstice , Thanks Frank