Howdy and Welcome to iRV2.
Glad you found us, theres a lot of RV talk here so I know you will find what you need.
As far as the cracks go, I am not sure if you mean on the trunk lid or the roof. I had some cracks start to show on the trunk lid of our 1999 Bayside and was told by the service guy it was because of the pressure of the locks we had them to tight. He said they only have to be snug and you should see the gasket go down just a bit not squished. If its in the roof the same thing would apply. I spread some RTV under the trunk lid in the corners where the cracks were just to be safe, a nice thin coat and its still OK.
Have fun and keep us informed on how your doing and let us know your questions.