Always best to find the leak(s) first. I seem to recall Egg Campers really only have a single seam across the middle of the roof and I also recall them as being double hull design. If that is the case it would reduce leak points to check a great deal.
I too would suspect plumbing for under sink. Or any vent/widow near there. Thinking
refrigerator air intake.
Once leak is eliminated and wood is fully dry it can be assessed for extent of damage. Dry it may not be as "soft" as when wet. Do some research by searching the forum into wood hardeners.
Worst case if the wood is not salvageable with a hardener there are some good threads and accompanying YouTube video's on replacing a small area of wood floor by cutting through the floor and the wood patch material at the same time. Patch cuts will be an exact match for the floor cuts done that way.
Then it is just a matter of using wood strip(s) across the hole under the trailer with wax paper or aluminum foil to keep glue and FG from sticking to them. This supports the patch while you apply crack filling adhesive around edge from above. Then
fiberglass patch in. Once it has been glassed on top the support strips get removed and one can glass it in on the bottom.
Patch should be as strong or stronger than rest of the floor done this way. Under the sink one wouldn't be walking on it so it only has to seal out elements and support the
weight of what is stored in that area.
I do not know how Egg attaches walls to floor. If patch is right up against wall there may be a need to redo some FG "tabbing" that attaches floor to walls. Think using FG resin and mat to "tape" wall to floor. That also sort of complicates cutting the patch to fit since one can't cut all four sides of the patch right through the floor. Just means you have to cut the patch, trace around it and cut out the floor along the traced line. I always end up with a bit bigger seam when I trace patch and cut. Not too bad but cutting patch and floor at same time always fits well.
Not a major structural issue by any means. Nothing that would make camper unusable or not road worthy. Just about the only thing on a FG molded that can rot is the floor so lots of threads on fixing that in the forum. Often floor can have damage from a leak that the owner doesn't notice because they are not going over it the way a new owner would. Small plumbing leak might go unnoticed with stuff stored under the sink. New owner finds, fixes, and good to go for many more years.
AC units move heat from inside to outside by pulling heat out of air inside and moving it to external heat exchanger (fins) where heat is transferred to the outside air. If the box is getting hot then the first thing to check is how much air flow is there at the outside fins and how much outside air is able to move across external cooling fins. The outside fins don't get their air flow from inside. The air that blows across the outside fins is outside air. Clogged fins or something blocking the vents where that air is pulled from, or a bad fan on the outside fins will let heat build up. Even though the inside air is cooled at least some by heat being moved to the outside heat exchanger.
Good luck and let people know what you find and how you fix. Your experiences help inform others and there are not as many Egg Campers as there are some other makes so what you do will will have value to other owners.
My Solo Trillium
Caveat Emptor
AbelEgg
2011 Eggcamper 
Scampy
Linear Mode
