We also have a 69' GT with I believe the same layout. We bought it used and refurbished a lot of it.
In regards to the shower we just bought a single shower curtain and hooked it up to the rails. We found it works well without the snaps. I am 5'10 180 so it is a little cramped but leaving the door open does provide a little elbow room. Make sure the curtain long enough to stay inside the base though. The toilet paper...we just take off for a shower. Not the best solution but it works.
As far as the front dining area goes we have the same set up. We are only two so we never need the extra bed. When we purchased our trailer the were some boards that were designed to fit the space in between. We tried it once to see but could never figure it. We actually removed the wood shelf from the walls too.
If you have any other GT questions I would be more than happy to help. Always nice to find someone who has the same unit.