'Lo, I'm very new to this Char G thing and don't even have a "ride" yet

I'm interested in knowing a few things and hope you guys can help me out.
1. Are there any 2G Eclipse bodys for these things?
2. Are there any differences in the car bodies other than the looks? I.E. The (insert car model here) is a ligher body, and it also faster and handles better etc.
3. When I do end up purchasing one, I'll also be purchasing an aftermarket motor *3.8*, battery, and tires.... Do the tires really help @ all, are there any other things that could help w/the handling aspect of the vehicle?
aaaaaaaand finally....
4. What's the proper technique for breakin' in these lil' motors anyway?
Thanks a TON for the help, I'll probably be buyin' this stuff tomorrow