Make sure you have good rubber; stock Conti;s kinda suck.
Next mod should be an intake.
From there, just adding a tune will make a huge difference from stock.
Next is probably a pulley (& re-tune).
The NeedsWings intake mani's look pretty good, too.
Make sure to increase cooling as you increase heat.

One simple thing might be to replace the steering stabilizer; they tend to go at about 15K miles.
Fogged headlamps and an easily fixed tans leak are also common.

BTW - I'd either buy in winter when toy cars like these don't move too well, or wait until late summer when the 2010 cars are coming out.