As just about all of us have read here, certain models of WW trailers have defects that have resulted in a number of different problems. To one degree or another, this subject has come up on this for...
I will clean the old TPO with Acetone before applying eternabond. It is friendly to TPO and epdm. Good choice from your roofer friend. Just use Kilz or Shelac on any mold. it will stop it dead.