Well it took me 13 hours.
So with a 6" lift you'll probably need atleast 15 hours. You'll need acouple of extra tools, like a die grinder or dremell tool to grind under the front aluminum 3rd member. You'll also need to grind off some of the metal off the rear lower shock mount. Other than that some axel stands, and a floor jack. Having a friend to help in jacking up the front control arms when installing the springs.
Also important to know is I beleive step 9 when you cut the metal insert for the front 3rd member mount. The instructions will leave you a bit puzzled. So this is what I interprated from the instructions. I took the insert, and cut off about a 1/4 inch or so. exactly half the thickness of the blue plastic mount "not the width, half the thickness" and it worked perfectly.
That's about it. Just follow the instructions step by step, and in 15 hours you should be done.
Oh and if you haven't worked out in awhile, you'll need your wife to give you a message afterwards. TRUST ME

If i missed anything I hope someone will fill in the gaps.