I just did that, basically, and will tell you that the plumbing is child's play compared to the concrete work. The experts here can give you excellent advice, but will probably want a fairly detailed description and rough sketch of the project to start with. I used CPVC for my supply lines, but if I had it to do over again I'd use Pex, probably Wirsbo (sp?), based on what I've read here. I ran 3/4" manifolds to 1/2" fixture supplies, but would run 3/4" to the shower if I did it again. It'd be tempting to run 3/4" everywhere -- with Pex, that might simplify the fitting and tooling requirements as well.