Installing a water manifold in my Big Country

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I am planning to install a water manifold in my Big Country this winter. I have reviewed the many threads and pictures in these forums and have a good idea of what to expect. My questions are"

1. Where is the best place to buy a water manifold. We will be spending the winter in Florida
2. Is it difficult to run the pex pipe up into the shower?
3. What were the main problems owners ran into during installation?
4. Looking at the pictures I got the impression some owners replaced the original tubing with Pex pipes without using a manifold. Is this easier?

Thanks for any help you can give me