Repairing roofs

Replacing the whole roof including some of decking (plywood) is a big job ! Definitely a 2 man operation. A third on the ground would also be helpful. Renting scaffolding would probably be worth the cost.

I had a similar situation. I discovered a soft spot after having a drip on the bed on a couple of occasions. It turned out that my vent cover had made a small cut in the rubber roof. I cut the rubber a few inches larger than the piece of OSB I was going to have to replace. I peeled the rubber back and cut the bad piece of OSB out back to the nearest seam in the OSB. I added some reinforcing where the new seam was not over a rafter. I then re glued the rubber to the roof and used eternabond over the seam in the rubber. The hardest part was finding the correct thickness of OSB. It is not a hard job if you have any carpentry skills and a few tools.

I repaired a corner of the slide-out roof in our 5er we had. The corner wood was "soft" and I cut away all that and replaced it with good wood, and repaired the roof part on top of it all. Eternabond and Dicor all over the place! :)

After the repair, it did not leak, but it was not quite right, because I created a high spot, and now a big puddle forms when it rains. Didn't like that puddle.

It might be better to leave the "soft spot" alone, and just repair the leak in the rubber roof. At least that way you will still have it level and not create a giant puddle that won't go away (until maybe it finds a way down--especially if it turns to ice and melts and ice and melts for a time)

It might me simple. By my personal experience with water damage in RV's is that it will be MUCH worse that it appears from the outside and will probably snoball into a massive undertaking.

I have never done it but, I wouldn't hesitate to open the roof, remove/replace the bad wood and reseal the roof.
However, I did a lot of home remodeling, building and repairs in the past.
It's all in what you're comfortable attempting.

Maybe you could rent a large garage or storage unit for a week or short term? And get a friend to help?
You wouldn't have to worry about rain if you needed to leave the roof open for a day or so while you waited for materials.

Get some estimates to have it repaired. Then decide if it's worth attempting yourself.

Now if it was my computer that needed repaired, I would drive over it with my truck and then buy a new one. :)
What's your comfort level?

I've never done it, but I'm with you that it doesn't seem that simple. I doubt if it really is since there are several sub-steps in each of those simple sounding steps. Plus, until you get into it you won't know how deep the damage is, which can really impact the difficulty factor.

I've repaired slide-out floors, toyhauler beavertail floors, and partial walls, but repairing a roof would certainly give me pause.