Good idea about adding a ducted vent. The vent pipe to the RV roof is probably a standard 1.5" waste line, so if you remove the cap it should be simple to connect a 1.5" light duty hose or pipe using a rubber union (it has screw clamps). Run the hose/pipe to any accessible outside access point.
A swimming pool vacuum hose or similar will do and is not expensive.
Former owner of 2004 American Tradition and several other RVs
Home is in the Ocala Nat'l Forest near Ocala, FL
Summers in Black Mountain, NC