I have the Werks (Howe) radiator on my '06. It's a drop-in replacement, except for the fan shroud which needs to be trimmed on the sides to fit. A Dremel with a cutoff wheel, masking tape, a Sharpie and a steady hand make short work of it.
But, it's a $650-ish radiator. Not sure what the stock radiator goes for, but it has to be less than that. The extra gallon of coolant and WAY more surface area really comes in handy for road racing, but for autocross it's overkill.
Could you elaborate on fins "literally falling off?" As in, they are LITERALLY falling off?
Electric water pumps have been done by a few guys on the Cobalt forums (they also use the LNF motor). It's nontrivial. A properly installed pump should last you ~100k miles on this engine. (Though others have had different experience, so let the tomatoes fly.)
Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders
'07 GXP, Werks Big Wheel K04 and tune, Solo catless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces, RPM rollbar