I assume you mean the Warn kit. Make sure you follow the directions exactly on the install procedure. Both on the order of parts going on (washer, then special nut, then other washer, etc), and in at least one place, you torque, then back off. If you do not have the instructions, I'm sure they are available at Warn's website.
Take pictures during disassembly, it helps knowing how they go back on when you have a pile of parts on the floor (but the instructions are pretty good about this).
Make sure you torque the allen head bolts properly as directed using IN-LBS, not Ft-lbs.
Make sure you use the proper specialty tool required, don't substitube needle nose pliers, etc.
Any of the parts you re-install (like spindles I think), clean them completely, pay special attention to the mounting surfaces, they should be clean of rust scale etc.
Good upgrade, I was happy I did it.