Dori, sorry about the loss of your DH. But girl you pack up and go. If you need some help you know how us campers are, just ask. What better way to make a few more friends. If you have questions, you already know where this site is.
Now for the bee's. I've found Sevin dust to be very effective for flying and crawling critters. I don't think it's good in your situation though. It would end up air borne in your living area, not good.
To enable working from the inside I would devise a cover that could be taped over the inside of the vent. Then with it in place, pull a corner down just enough to give them a quick short burst of wasp spray and seal it back quickly. Leave it until the next day and repeat for a couple of days. I would like a clear plastic cover that could be seen through just so I could watch but even cardboard will work. Once your sure there's no activity you can remove the screen and with some heavy gloves remove the nest and drop it into a plastic bag.
Some of the idea's on this thread are truly creative. Leaf blowers, vacuum cleaners and CO2. My experience was to run over a nest of Yellow Jackets with a bush hog. A one legged guy, pulling the kill switch, jumping from a moving tractor, trying to run through a corn field while pulling bee's from his hair is not a pretty picture (quit laughing). Over a thousand bee stings, some baking soda paste and a shot at the emergency room, never felt a bit sick (just stupid). I would not recommend this procedure.