Tony
The first big thing is do you want to re-do your whole shower. I would tell you yes. It sounds like it would be cheper in the long run to:
1. Inspect the shower valves for leakage. If leaking, repair that and the loose tiles.
2. OR remove all the tile and drywall.
3. Now would be a good time to replace your shower valve if it is older.
4. Consult with a bathroom design store about a one-piece shower pan. Not to worry, they can cut the drain in any spot in the one-piece pan.
Or have a plumber install a shower pan(it is a thick flexible polyethylene–glad trash bag- material which a plumber can cut in any place for the drain.
5. It is rather easy to move the plumbing for the shower drain to be more in the middle of the shower pan. wether you have a slab(concrete floor) or a foundation.
Good Luck
