Along with input from members that have had delam issue do a google and youtube on the subject. I did a quickie and looked to be dozens of videos on the subject of how to fix or how someone fixed their problem.
Much has to do with fixing a water leak or other reasons it delaminated.
Without seeing the delam area and poking here and there looking for structure issue we can only speculate. I would get more than one professional opinion or estimate.
"good judgment comes from experience, and a lot of that comes from bad judgment" ............ Will Rogers
'03 2500 QC Dodge/Cummins HO 3.73 6 speed manual Jacobs Westach
'97 Park Avanue 28' 5er 11200 two slides