Yeah, that is the biggest thing.  Make sure you have everything.  When I got mine I had to buy it all in seperate pieces because at the time Pro Comp didn't just sell a kit.  Now they have their Stage 1 and Stage 2 kits.  Most kits don't come with an SYE or CV Drive Shaft but almost all kits have everything.  Things to look for, Adjustable Track Bar, T-Case drop (if you don't plan on getting an SYE right away), Sway bar disconnects (optional but a lot of kits have them now).  I think that is the most common pieces that are left out.  None of them you absolutely NEED, but they are VERY good to have.  Any questions just ask.  I think most of us have installed a lift or two here we we kinda know what we're talking about.