If you tell us what year Jeep you have, it would help out some.
At around 3.5inches is the cutoff for needing a Slip Yoke Eliminator. If you do experience some vibes with your kit, then you could try a 1'' Transfercase drop, that drops the Crossmember and transfercase down to aleviate some of the angle on the driveshaft. The transfercase itself and rear axle play a role in whether you will get vibes or not, which is where knowing what year and tcase would help.
If you decide to disconnect your sway bar up front, which provides a smoother ride offroad and more articulation, then you might have to worry about the length of the brake lines up front. You can buy new, stainless steel ones that are longer, or you can search around for how some people have relocated the line to provide for more length. I can't really think of much more you would need for a 3 inch lift.
As for brands, what are you looking to spend on the lift? If you want a smooth ride, Old Man Emu puts out a quality product, but its more money than some of the other kits. Rubicon Express is a little bit more expensive, but they provide more complete kits as well as a top quality product that many people on this site run, and swear by. Then again if you want something a little cheaper, you could go with Rustys, Ruff Country, or Tuff Country. Cheap kits that will provide you with lift, but with a little rougher ride.
If you search around for Rusty's on here, you will get a bunch of reviews, most bad, but some good. For what you will be doing, it would probably be your better bet. Relatively inexpensive, and will probably be good for your type of offroad, where its not as hardcore as rock crawling or some of the other areas.
