it's true you can learn how to make waterproof supply pipes, and it's also true that every homeowner has the right to work on his own house... it's a bit late to learn this now, when you want to build your shower again and have it working soon. (Supply pipes can leak later, after they first pass the test). So there is every reason to hire a Master Plumber for what will be a clear cut operation for him/her. For the pipes and fixtures. You have to know in advance what method you will use to make your walls and waterproofing because he needs to know how thick your wall will be once built.
About waterproofing tiled walls: check out these options:
1.) Wedi,
2.) Kerdi,
3.) the trowelable (liquid) waterproofing membranes like Redgard, Mapei HPG and others,
4.) the use of a plastic sheet under CBU.
A plumber will tell you that you need waterproofing but he won't install it. This is a good project for DIY. Caddo, since you haven't mentioned any foul smell, I guess you didn't have a humid space inside the shower wall cavity. Depending on your climate and your building, it may be really really important to ensure that your new shower be waterproof. You want to build it right or else you will be breathing bad air all the time once mold grows behind the tiles.
David