Here's what I've found. The replacement fan model number is 2250 and the best online price is $217. I'm trying to set up an appointment at an RV repair place I've used. They're already booked into June. I think I can drive with the old one maybe after taping the cracks. So I will wait to see if the RV shop wants to buy the vent and charge me a premium or if I should buy it and have them install it. That would be fine. I could try it but I'm 71 with cancer and a replaced hip.
The muffler shop guy said he has not had a chance to try to get the van started. If he fixes that I may still be able to go to PA tomorrow. But I am still doubtful.