The first thing that I would recommend is getting yourself the lower aluminium chassis plate and immediately change out the original plastic one. This is a known weak point on all of the Mega line,as any good hit on the front , has a habit of snapping off the entire front end. Have a look around for aftermarket shocks,you'll find lots of ideas throughout this forum,along with better rear tyres.
In general,very few parts break on these trucks as they're very well built. Normally a common spare part are the A-arms,but not on this range,I've yet to hear of someone break one. Diff oil:- 7000-10,000wt. Shock oil:- minimum of 350 cst for both. Hope this helps Madmax.