Re: shower replacement/refitter?
If the tile is cracked, odds are that it's already been leaking and the swelling of the substrate has caused the cracks. IMHO, you're pretty limited as to what you can do because if it's wet already, they you want to open everything up to let it dry and replace the wet/damage. The only way to know if it's wet, and certainly, the only way to fix the tile is replacement.
You could cover it up with an overlay, but then you haven't addressed possible moisture problems that will continue to degrade the wood and substrate for a very long time. Overlays are only for applications that you are certain are stable.
Your least expensive replacement option (after removal of the old ) would be a full fiberglass insert. Next option would be a fiberglass pan with tile or a cultured surface. Most expensive would be a full tile or cultured unit.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!