the motors are really easy to change
all you have to do is pop out the rear gearbox and then open the 4 little tab thangs around the edges then pop out the motor put the pinion gear on the new one and pop in its place and reinsert the gearbox
a good site is
www.tinracers.com
I ordered a bunch of stuff from them
motors are a standard 130 size so tamyia mini 4wheel drive car motors which you can buy at most hobby shops fit ans are very good
the fastest is the plasma dash
I have the hyperdash and it has lots of tourque and speed
to put in a faster motor you really should get relays first though
then a new gear box and wheels with ballbearings
if you have any more questions just ask
I can also sell some motors which are like the red black ones on tinracers site
nick