I own 4 duplexes and each one has reached the age where the shower tiles are starting to fail. In two cases I have tried the fiberglass surround approach and I’m unlikely to try that again. In a perfect world you should be able to just knock off the old tiles and glue the fiberglass sheets back up, but in the real world once you remove the tiles you will probably find a nightmare of rotted drywall, moldy insulation and even rotted studs. So now you are no longer looking at a quick afternoon fix, but a major project.
Even so, for the average DIYer the sheets would be easier to install than retiling.
And then there’s the pink tub. I’ve had to replace a tub once and it was the most difficult DIY project I’ve ever undertaken. Most bathrooms are very compact, and you don’t have much room to work in. To remove the old tub you will need to break it up by sawing it into pieces or busting it out with a sledgehammer. To get the new one in, you’ll need to tear out the walls down to the studs. Now you have to manhandle the new tub through doors, around the sink and toilet, and drop it into place with virtually no clearance. Now you have to reconnect the plumbing. But wait! The tub now blocks access to the plumbing, so you have to cut a hole in the wall opposite the tub to get to that. Well, as you can see, it’s not an easy job.
It may be easier to just learn to appreciate the vintage look of what you have now.