Of course it can be fixed. Don't let the con man con you. The leak could be
something as simple as a leak in the shower drain pan if it is a shower stall
or the caulking between tub and tile in a full bath. Can you get at back side
of shower water supply? There is usually some kind of access panel in a closet
somewhere for this reason. Your shower valve could have a small leak also. No
need to remodel the whole bath in any of those cases. Shower pans can be
replaced it's difficult but can be done if thats your case or caulking is
easily replaced if you have a tub. If it's the valve thats easy to replace
also.