You can do a lot of different designs and be really creative, but keep in mind, the resale gets majorly killed so make sure you will have the gun for a very long time regardless before proceding. No, it's not hard, just don't rush and be sure of what you want before you start as there is no going back.
You can indeed damage the gun if you go too crazy and, like RTF frames on glocks, the feel might not be for you, so look around to see if you really like it before you try it, or do a test stipple on an XBOX 360 controller first.
I agree, it's not something to rush into. I'm not concerned about resale value because I plan on passing them on to my son when I pass on. I must say that I've had 3 other officers now ask me if I'd give theirs the same treatment for money. I'm thinking about it, but will consult with an attorney first as well as finding out if my personal liability insurance rider would cover any possible damage which may occur.