Ian i just did a ballast upgrade with WM and reversable pumps as well. I can answer most of your questions, you will end up with extra parts, they ship a few extras so you have some flexability on how to do your install.

Try not to get over whelmed with the amount of things they sent you, you just have to break it down to each section.

If your planning on using 1 reversable pump for the bow then you should have a Y valve in a box. This allows you to control what bag it fills and drains in the bow. I use 2 of these in my boat for the 4 bags in the rear of the boat.

Shoot me an email at [email protected] and i should be able to help you threw most of your stress, and i can give you some ideas where to mount pumps and threw hulls.

I think i even have a thread on my new ballast system with pictures on the threw hulls and such.