Manufactured home bathtub/shower wall installation
I have replaced dozens of older tub/shower units with nice fiberglass tubs with a three piece matching/interlocking surround wall kits. Since getting a one piece unit into old construction is usually impossible, these modular units work well. The better units are sturdy and will adapt well in situations where the walls are not perfect. Since the wall units interlock and overlap the tub flange, leaking is rarely a problem. The costs of these units run from about $500 to $800. I have good results with Kohler and American Standard units. Avoid the cheap units that have non-locking wall sides and require a lot of sealants and flimsy corner trims. This is not an easy DIY project for someone without experience. The process will include plumbing skills, leveling the tub unit and shimming the walls if the existing wall framing is really bad.  Sometimes it is necessary to remove existing wall sheathing (drywall etc) and attach tub and sides to studs, then use moisture/mold resist drywall to recover the walls.