While I had all of the cooling lines disconnected for our engine replacement, I decided to replace the water heater at the same time. I was not sure how old it was, and I also wanted to fix up the mounts, so while I had it out, I put in a new one. I chose the Seaward 6gal model that looked like a direct replacement.
To get it out, I had to remove the galley drawers frame completely. Even then, it took a lot of turning and angling the heater to get it out. Once it was out, I removed some old hoses and cleaned up the area a bit.
I then built a new mount that would keep it more secure, and wedge it up under the dry storage locker to keep it from moving. I also chose to turn it around so all the connection were on the forward side where I could access them better. This meant slightly longer hoses from the engine, but made it much easier to work on, since they faced the open area under the main settee.