It easy, but depends on what size you want. A lot of us have gone with 10"and 12" ape hangers. No need to Change any cables,,, but anything bigger youll be getting into cables and extended wireing 'some times it's only the brake cable/line.
But there's lots of info on here.
It depends on what you want to do....if it's a straight bar swap you may only have to drill a couple of holes in the bars for the locating pins on the controls. If you are changing bars and risers you will have to consider size, width, height and pullback. This will then effect clearances for your tank and cable lengths.
I totally agree with all that the guys are saying. You can make a bar swap extremely simple and inexpensive or you can make it really nice looking and and expensive with how detailed you want to go. I am currently in the process of switching my stock bars on my 03 volusia and replacing them with 12" apes. I've decided I want to go as clean as possible so I literally am replacing everything from triple tree up and running wiring internal and all stainless coated cables including brake line, handle grips, chrome housings, brake reservoir , mirrors and levers. I have spent a very fair amount of money doing all this but like I said it's the look and comfort that I want.