The tub/shower unit seems to be made of acrylic, has no lines and looks like it is only one piece. I would like to replace it with a newer version with higher walls. Is this possible and if so how?

Then, order your tub. Acrylic replacement tubs are light enough for one person to lift in and out, even in tight spaces. Beware of one piece bathtub shower surrounds and one-piece tub/shower stalls.

Bath Fitter creates a bespoke piece of acrylic (or whatever ... Bath Fitter can install your new bathtub or shower enclosure and walls in as little as one day. One reviewer, Ingolf in New York ...

When installed with a one-piece seamless wall system, these acrylic tubs and showers look new for longer than most traditional remodel options and are backed by a lifetime guarantee. Myth ...