I have TJ Flares waiting to be put on my YJ, and I've been contemplating this very idea myself. (TJ Flares = more clearance for CJs/YJs).
The only difficult part is really getting the cut correct without burning the paint, and mounting a new light fixture, but it's really just a matter of doing it.
As far as support goes, your current fenders aren't anything special when met with a tree, and these really aren't that much weaker. If you need support, go tube fender or just don't care about how it looks imo.