just got some 3:73's that are fairly new (just the gears), and i was wondering what else im gunna need to install them,
fluids? or anything else?

 

Get sythetic gear lube i recommend Amsoil. Also you are going to need a new crush sleeve and shims. I recommend all new bearings and axle seals and pinion seal. You will need a new gasket and marking compund to check the patttern on the gear. I would try the install unless you really know what your doing. Its not hard its just you need to make sure everything is right ex. backlash, pinion depth. Certain things you are going to need special tools for. Good Luck!