On ours, I had to replace the whole assembly, not just the tank -- a quirk of the Suburban design, I guess. Everything is one piece.
A trip into town to use the library's free internet to get the number of a mobile RV repair company that I know about. A quick call told me that their fees would be prohibitively expensive. Another search to find the names and locations for RV parts places. One was a dealer in a small city about an hour away. We drove there, and they said they don't have any water heaters in stock, but could get one in in a few days, but that was the day we were going home. I ask them if they knew anywhere else I could get one. They gave me Len's Alternative RV Sales
in Brandon MB (I highly recommend them!) and they were only a short drive away. We found them quite easily and they had a stack of water heaters in their shop, new in the box. We bought one and brought it back with us.
Removing the heater from the trailer was easy. Disconnect the wires (I took a photo of the configuration before doing so), shut the gas off and disconnect it, and remove the two water lines. Then remove the dozen or so screws holding the heater in place, and pull it out. But the big problem was removing the brass fittings that connected the water lines to the heater. They had pipe threads on either end, but the end that threaded into the tank was seized. I had to cut the rest off and drive into town show it to the guys at the hardware store. Me, not knowing any better, accepted what they sold me which was totally wrong, and took it back just to find out it wouldn't work. Another trip into town to exchange it for two short galvanized pipe nipples which did work, back to the campground only to find that the pilers I had weren't good enough to tighten the fittings into the new tank, so back to the store for a pipe wrench -- I thought ahead this time and bought a few more things I thought I would need, and I'm glad I did. Once I had everything I needed, it was a pretty easy job of putting it all back together.
Basically two days of our vacation gone to do a task that I could have done in an afternoon had it happened in my driveway at home. The next time DW asks, "Why is there water running across the floor?" I guess I'll know the answer.
And the problem with the old water heater? It looked like water somehow infiltrated in between the tank exterior and the styrofoam insulation, and rusted the tank from the outside in. The anode still had over 50% of its material left.