Replacing an old tub with a new fiberglass tub and shower surround is not as hard as you think. For remolding jobs, there are new two piece tub/shower replacements designed to be able to fit through the typically smaller bathroom doors.
The first job is to remove the old tub, which will be messy, so be prepared. Take a rag or duct tape and cover the drain to keep debris out. Before the destruction phase, turn off the water supply lines, both hot and cold water lines. After the water is off, remove the small end caps from the handles and with a screwdriver remove the screw and then each handle. With a pair of channel lock pliers and a soft cloth, unscrew the spout, being careful as to not scratch it. After this is removed, using the same pliers, remove the shower head and pipe.
Now, carefully start to remove the shower walls by using gloves and a small sledge hammer, knock out piece of the existing wall, right to the studs remembering to remove all the screws and nails. It is important to take care in and around the tub faucet and shower head, leaving the existing plumbing in place to be re-used later. Now for the tub removal, an old cast iron tub will break apart with a little force, or if there is a big enough window or door, remove the drain and spout and with help remove the entire tub.
With the tube removed and the shower wall area completely striped back to the studs, make any repairs needed to the flooring, plumbing or existing framing. The new tub should be in two pieces, the tub and the shower walls, all three sides, as a second piece. This will have only one seam at the top of the tub, but hidden and leak free. Position the new tub in place, propping up one end to connect the drain to the new tub then slowly position into place. Follow the manufactures instructions if you need to drill a hole for the spout.
With the tub in place, bring in the shower wall section, and again follow the manufactures instructions if you need to drill a hole for the faucet and/or the shower head. The tub and shower wall unit is designed to interlock with a leak free single seam for a clean seamless look. After the wall section is installed, using new ‘greenboard’, a water resistant sheetrock designed for bathroom, patch in at the top of the shower walls as needed.
With the faucet and showerhead re-installed, turn on the water and test the new tub. That should be your new bath tub successfully installed!