We have 15 year old panels and lids/doors that seem to work today as they did when they were installed. Alas, Glacier Bay went out of the business. I think there's a follow-on company, but I haven't pursued it myself.

These were premade sandwich "vacum" panels. You can't cut, puncture, drill, spindle or mutlate -- or they have insulating properties of tolet paper (I could have used a different variation on that. ;^))) ).

They were very expensive at the time, but I think worth it.

My adivce: If you don't use a prefab vacume panel from a very reputable company, then go with "blue board" with a sealed box constuction. It will probably invovle taking the existing box and rebuilding it. If your box isn't holding, you should get that goo out of there. I'd be surprised if wasn't filled with mold, and other elements of the "goo of life".

My views: If your cold box is only used on weekends and is usually at air temperature in between (the normal "ice box" on a cruiser of old), then the insulation isn't that critical. But if you plan to keep the box cold for extended periodes, then you really need a hydroscopic foam (Blue Board, not just normal Styrofoam or Bead Board or spray-in insulation), and you need to provide vapor barriers and ventilation or you'll be growing stuff inside your boat.