i have read the instructions for installation, but i also know that people will find shortcuts at times with great results. here are my questions: i am installing on a wall formerly occupied by tile so the tile (adhesive? it doesn't look like mortar) is still on the gyprock which it turns out aside from a number of small tears of the surface paper, is is great shape..no holes..is there a way to smooth that adhesive without tearing the surface..or even if i couldn't, could i put a tar paper/lathe\mortar on top of the surface without tearing out the existing gyproc and replacing? if i could obviously the job gets much simpler. secondly, if i did have to cut out the old gyproc, how do i cut it out without tearing into the vapour barrier underneath the gyproc? thank you..