Depends alot on the skill of the wrench turner and familiarity with body lifts, by myself I can normally do one in a day (8hrs) on most any Dodge, or Ford, newer GM's can be a bastard. Dak's aren't that bad, follow the instructions CAREFULLY, a small f-up on a body lift can cause lots of headache, and when they say watch for binding/stretching of lines/wires they mean it. Other than that, not too bad.
That being said, I have sold 3 in the past couple months to customers that were planning to do it in the driveway and ended up bringing it back to be installed. And as many or more to customers with no problems with a self install. If you get into it and need advice/help/whatever I've done more than my share give me a ring. I'll be glad to point ya'll in the right direction.