Assuming there's no structural damage, it's pretty easy.

I've removed the entire front bumper (upper portion and lower air-dam) to replace some other parts before on my 850.

I've since replaced the stock air-dam with the "R"-type air-dam. The attachment points are identical, so no problems there.

As I recall, it's basically just a bunch of bolts & torx screws holding things together. I think the wheel wheel liner is attached with plastic rivets. Just start from the top and work your way down, looking for the various fasteners.

I also recall something about a plastic rivet or bolt somewhere in the center of the bumper assembly which I couldn't figure out how to remove.... it broke off in the process, and I've never replaced it. Never even noticed it's missing since then.
Good luck!