I wanted to put a new mirror cabinet in my washroom but the one I bought is a little bigger than the one I have. There's a back splash that goes from the ground half way up the wall, so the new mirror cabinet will overlap the tile. How can I make a clean cut to perfectly fit in my new mirror? Also the back splash is not the like a kitchen splash the tiles are individual and a lot bigger so it shouldn't be a problem. Can anyone help? Thank you!