I plan on buying a prepainted GS 400 style spoiler for my 01 GS 300 (white). Do you all think the paint match will be off any, since the car's paint has a few years on it.

 

It will probably be off some due to your paint being exposed to the elements, especially fading due to sun. I am picky about the paint so I would probably have it repainted to match. You can always buy it and see how it matches, and if it is way off you can get it repainted.It should cost more than $100 or so

 

I think 01 White is crystal White...so the color won;t that off since they don;t fade like pre 01 model's pearl white...
you should be OK... I would try to get it prepainted and see the difference