Since you are already taking apart your ballast, getting to the shower hoses will be very easy.
To take apart the ballast, all you need are a standard flathead and phillips screwdriver. There are three hoses that go into the ballast sack -- the fill valve (on the left/port side of the boat), the drain valve (about 4" to the left of center at the bottom of the bag), and the overflow valve (in plain site at the top right/starboard side of the bag). Each of these is connected with a screw-on clamp that uses a flathead screwdriver. Then you need to unscrew the fabric cover -- just two phillips screws towards the front of the trunk compartment.
Once the ballast is out, on my boat there are two large thumb-screws in the floor. Unscrew those and pull from the bottom, and you will have access to the hoses for the shower. Red is hot, blue is cold, white (or black?) is the shower outlet. If I remember right...
My ballast sack was about $275. But well worth it and much nicer quality than the stock bag, and it will never have to be replaced again. It is made out of river raft material so no cover is needed and it will not expand like the stock would. When it's full, it's full.
Good luck and let me know if I can help with anything else.