Ted,
My 2407T had a leak like yours right at the flange of the blackwater tank. I managed to fix it without removing the tank. The process is described here in the forum as well as on YouTube. The toughest part for me was grinding an ABS fitting to create a thicker liquid ABS to apply over fiberglass screening. I was temped not to do it myself, but it turned out to be an easy fix. I cleaned the work area well, applied a layer of patch, waited a day, repeated to add an additional layer, waited another day, and applied a final layer. It is much stronger now than it was when new. Each layer smoothed itself as it cured and the final result looks professionally done (IMHO).
Read several of the how-to threads, ask questions, get answers, and have at it.
George