Replacing a shower enclosure is a job that requires a great deal of consideration. The job itself is not particularly difficult, although it is a 2 person job. What is more difficult is what you will find underneath. Everyone will know that removing a fixed object from a wall can damage the wall under it, but you can also find old mistakes made in the previous installation.
Do make sure that the shower enclosure you buy is an identical fit to the one you are replacing. If the shower stall is a fixed size, and you are not able to increase the dimensions, you will have to work with what you have. Be careful when you remove the existing stall enclosure. You do not know what you will find behind it, and you could end up bringing half the wall with you.
Don’t buy a poor fitting enclosure. If you buy an enclosure which is completely unsuitable for the space you are filling, it will result in having to do far more repair and remedial work than you would have done if you bought a proper stall. Don’t forget to turn off the water supply before you start. You will be removing the entire shower unit; water spraying all over the place is not good.