Hehe, I just bought one of these on a whim while browsing a local-ish Action Model Center in Torquay. For £109 all in, I know it's effectively toy grade, but with 4 wheel steer options, and about 75 degrees of articulation it's all fun so far in my living room! I've already thrown out the foam mouses from the tires and softened the suspension a little. There is oil in the dampers but the chassis and shell are so light that it just bounces off the floor when dropped from 12 inches up.
The on/off switch is actually soft neoprene or something, you have to squidge in and hold it to switch it. And the central lower half of the motor/diff housing is removable, presumably for servicing or repairs/replacement. There are four different sizes of ballraces in the spares selection and I've already seen the inner/outer drive hub ones, so the others must be at the inboard end of the drive shafts and in the gearbox. Hmm, hang on, I'll check. Nope, can't get the steering hub carriers off as the drive shafts coming out of the diff casing have pressed in metal pins for the PLASTIC STEERING DRIVE CUPS. So I can't move the carriers out far enough to separate the diff/motor casing!! I'll do it if I have to, but not right now thanks!
Anyway, despite having a goodly bunch of ballraces, it's still a toy with plastic drive cups with no optional metal upgrades. Do any of their others have metal drive cups? Maybe they'll fit.