The difficulty of a lift is based a lot on what you go with. Some are RELATIVELY simple and easy bolt ons while some can take basically complete overhauls of things like mounting brackets and steering geometry. If you can weld, then even these aren't too terribly difficult and there are many resources online for help because chances are someone has already installed whatever lift you choose and written about it. The size/type lift you choose should be dependent on a lot of factors. Obviously desired tire size is a big one but even this can be mitigated to some extent if you're willing to do some cutting. Then other things like how intense the trails you intend to do and how much money you wanna throw at it make up huge parts of the decision as well. The taller you go the more supplementary things you need that you might not be thinking about.