BRAKES !!!! Has to be #1 for sure.
Then I would go with front fork springs, then tires.
Any other mod after that I think is more personal preference. My bike has never had the fix to the steering done. Ferbur fix. I hope I spelled that right. It handles fine so - If it ain't broke don't fix it. It may have more to do with the bearings than the rubber washer....that's my opinion.
Other than that, I'd say put in the manual fan switch and maybe the thermal switch although I never replaced mine just cleaned the crap off it. More comfortable seat would be nice.
I'm in the process or polishing all the aluminum parts, scoops, rims, levers and ect... I think it will look great but it's allot of work. But it's a mod that's cheap to do and I'm not riding it now anyways...