The shower style and fixtures should co-ordinate with the remaining items in your bathroom, unless you are replacing them too, in which case select a shower tray and wall panels to match your complete look.
Budget for all associated costs before starting the project. In addition to the Shower Tray and Wall Panels you will need a Shower fitting and a professional installer unless you are able to do the fitting yourself.
How will you dispose of your existing bath and fittings? You could arrange for your installer to remove this for you and dispose of it in a responsible way, otherwise you may need to hire a skip or arrange for a way to take it to the waste site.