Tub Surround and wall board issue
 

I needed to replace my 40 year old tub faucets. Seeing as the fixtures back to the chimney (IE no rear access) I had to go through the wall. My wife decided that since I was doing this anyway, we should get rid of the tile and replace with a 5 piece tub surround.

Plumbing is done. Tile removed. Now I have the walls. The paper on the walls (was green board) is pretty much gone. There is still alot of glue on the walls as well. I need to replace drywall where the faucets are. I also have a few smaller holes where my prybar went through while removing the tile (these are sporatic). Do I need to replace all of the wall board? Can I just seal it and skim coat it? I am hoping to get this done soon but if I don't HAVE to replace the wall board, I'm thinking that would be best. As I said, I will be putting up a 5-piece surround over the walls (Some 8x12 tile around the top as well).

The greenboard should not be used at all. I would remove it. Especially since you will not want to install any tile on this stuff. And a five piece tub surround means it is a cheap one which will leak at some point.

Does this advice have any experience behind it or is it just some spouted verbiage ?
Please state your past experience in remodeling and why you would use wallboard and what do you consider , "sealing".
Ron