Some stuff to remember:
Drain the coolant from the radiator first before starting anything else; that's so you can avoid a mess when you go to pull off the throttle body. The throttle body has coolant passages flowing coolant from the UIM.
Make sure you replace the plastic coolant elbows and THIS IS IMPORTANT: apply silicone grease to the elbow o-rings before you install the elbows.
Apply Permatex 2B to the threads of the LIM bolts. I'll explain more later.
Make sure you have an accurate inch pound torque wrench! Snug the bolts by hand first. Make at least two passes with the first pass at half the final torque.
UIM kit with included gaskets (it might include the elbows)
LIM gaskets from a GM dealer (make sure they're reinforced)
Throttle body gasket
Silicone grease or dielectric grease
Distilled water and new Dexcool
I'll post more info as I think of it.