well if its a gas job the first thing i would recommend is getting a good fuel that has after run oil in it that way you dont have to add it after every run also keep your eye on the spur gear unless it is already upgraded the plastic ones dont last very long, also the air filter will need to be cleaned the best way i found is to use brake clean and rinse with water and allow to dry then you will need some air filter oil and give the air filter a generious coating of it, as far as the diffs go i believe there is a oil in there im sorry but im not sure what kind or grade im sure your local hobbie shop can help with that, and the dog bones being loose is kinda hit and miss iv had my earthquake3.5 for a week and mine have a lttle play in them as well but they are not super loose if you deside to change diff fluids that would be a good time to check up on the dog bones hope i helped a little bit.
P.S i am new to the rc trucks as well, but being an automotive service tech helps