First choose a new name for a car set (i.e. paintkit cars96)
Find the car you want to change select it and click Export.
(Let's say you choose the 50 car)Go into windows,then file manager,view
the Nascar directory for the file named nasc50.pcx if you don't want the
file delete it.
Find the car you want to replace that car and rename it the same name as
the file that you exported.
Move the new nasc50.pcx to your Nascar directory.
Go into your paintkit (i.e. paintkit cars96)find the car you exported.
Select the car and then click Import.
WOW! well hopefully thats what you'll say.
You should see the new car in its place.
Don't Forget To Save It!!!!!!!!!!!!
Your Welcome,
jUsTiN