Ive abused my HF for aprox 3 yrs and only stripped the spider gears once. I still had the grease in the diff when it stripped. Once you put the diff oil in you should solve that problem. The spiders do have small shims behind each one so make sure they are there or add more ir required.
Thicker centre diff oil gives more all wheel drive and better accelleration/topspeed but less turning ability. So if you are gunna race on a track try the 7/10/3, 7/15/2 or similar. This should limit the front tyres pizza plating. The stock tyres are only ok for bashing and wont grip very well on most tracks. The also pizza alot.
Remember shim the pinion and crown.

I will be blunt. The HF is heavy and poor quality. It takes alot of maintanence. I still love mine though.