I am planning to install new shower and bathroom faucet for my condo. New shower one I am getting the one with handshower extension. Also existing faucets shower-to-bathroom faucet know is extremely hard either press down or lift up. Anyways I am looking through couple in homedepot and pick up as similar one as I have to reduce the efforts. I saved the exploded view of moen product below and looking at it wondering if the size and compatibility of the new one would match the older plumbing. Is there are standard sizes? I am specially concerned with shower tub and bathtub switch. I am hoping to install without gettin behind the wall with existing plumbing parts protruding from walls after removal. I am still going over product manual spec to see if I can glean something out of it. For existing ones, I can see the faucet and switch for bathtub might be easily removable as I can see the screws but I dont see any around shower. I tried to twist around pretty hard with reasonable force and it does not looke like it is going to budge any time soon. So I decided to ask here before I break something. Thanks!