[prairieschooner]

Respectfully disagree, if you have Suburban LPG Heaters a shop vac will not work, our older coaches are very different from the newer ones. Do not try to remove the exterior fitting, this would most likely give you an issue since these parts may not be available. Be very careful about how you get the heater out as well, I think that I had to take the one under the couch apart in order to repair it. I think that the others (under the Refer and in the bedroom closet) came out as an assembly.
You will need to remove the heater to gain access to the fan area if there is anything in there. On mine the wasp nest was inside the fan blades and the only real way to clean it was to disassemble and remove the nest. If you don't get all of the junk out, you may burn up the motor and that will cost you between $50.00 to $100.00 in parts alone. The Fan only circulates air from the outside across the heat box and then through the coach.
Hopefully you can do the work yourself, if not I think that I had about 1 1/2 hours to get the first one out and the others came out in around 1/2 hour. The first one back in took about 1 hour and the others about 1/2 hour each. I was able to find parts but they had to be ordered. Be very careful because some of the parts are not available (sheet metal and burners for sure).
I installed screens over the exterior to inhibit this in the future.