I bought a new to me TT that is in really great shape and had very few areas of de-lamination. I noticed that the dealer the folks I bought it from who they got the unit from a year ago, went over it ...
Yes you can probable DIY but the tricky part is as you stated 1.5 of water column..... to much pressure and you open up leaks that would not normally be an issue....If you can find a service center that does the Sealtech Leak Test that would be the next best thing !