To get the foam of the wheels which was very well glued on. I just cut the foam with a modeling knife taking off as much as possible. Then i ran the wheels over some sand paper as if truing the tyres until all the foam was rubbed away. Then i put on some new scaley tyres (xj220) and then trued them and it's been great, handles really well.
The wheels are connected to the axle with a screw (allen key head) so replacing the wheels and tyres should not be difficult , theonly reason i didn't replace the whole wheel and tyre combo is that i really like the wheels, so i just replaced the rear tyres.
Hope this helps