Jayco rear corner delamination

We own a 2000 Jayco 266 FBS and It's been a fine TT. I've owned 3 Jayco's with no problems till now. This sounds really odd but it happened to my TT. I store my TT outside next to a 26'x14'carport added to our house in 1982 when we bought a 1982 Coachmen. Since the Jayco has a slide-out it's higher and will not fit in carport. I had an electrician add a 110v 30 amp RV type receptacle in the carport to keep the battery and other things in check. Last fall, 2013, when it was time to winterize, I pulled the shore line out and connected to the 30 amp recpt. All went fine and I closed her up for the winter. I always push the cord through the wood louvers on the carport, keeping it elevated thru the louvers for water drainage. Then I route it through the rear ladder to form a good downward drip loop before entering the hatch, keeping water out of the cable hatch. Somehow during the fall and winter the shoreline entering the cable hatch of the TT became taught. After going thru the ladder to keep it off the ground it without my knowledge was pulled almost straight up the side of my TT. I'm not kidding here. Water ran down the cord and followed the shoreline into the cable hatch and into a storage box inside a closet. Now the rear corner near the hatch has seperated from the side and back corner up the side about 2 ft. I suspect water damage has occured in the floor and on or near the rear outside apron. I had to do something so I had my son help me force the metal ends of the corner together and used some foil duct tape I had to stop any further damage. Does anyone have suggestions as to repairing this?? I suppose I could take it to an RV shop but I'd rather take care of this myself.
Thanks for any and all replies.