prepping for bath surround

old tile out- put up "green" drywall (now purple)- Where the old tile ended (and old wall) has some larger gaps where it meets new drywall- I am wondering of the 60" high surround will cover- If not- How do I fix?? Any suggestions on tub surrounds that may be a little thicker soas not to have any imperfections from drywall show thru? see photohttp://s686.photobucket.com/user/skinut2234/media/IMG_0281_zpsi61uoce6.jpg.html?sort=3&o=0