In the fall of 1991 I bought a 1972 Jayco 1208. It was a piece of junk that I paid far too much for. I knew nothing and learned a lot. 3 corners of the floor had to be rebuilt.
Yes, this is a big deal. I hope you are handy. Where the floor is rotted you need to remove all the cabinets, table, etc. And if the rot goes to the edges you will also need to remove some of the inside paneling. You can cut the sections out with a jigsaw. The new sections can be secured with long sheet metal screws into the frame.
Most important. As you tear this apart you will need to identify where the water came in and fix it.
