I pulled a tandem axle pop up trailer over that road several years ago. It is very scenic but somewhat challenging. Snow was still present in shaded areas at the summit of the passes in early June. My daughters, being raised in Southeast Texas, got a big kick out of that. Cliff hugging roads with sharp drop offs and no guard rails. When we drove by, they were in the processes of retrieving a car which had gone over the side and down the mountainside quite a ways. Be sure to use your gears rather than brakes on downslopes. I did throughout the passage, but got over anxious and used the brakes as we came down the last section of road into Ouray. I could smell my brakes after we parked in town.
I would not attempt it with the larger fifth wheel we have now.
By the way, as I understand it, the "Million Dollar Highway" nomer refers to the cost of the highway and not the precious metals in the rocks they had to excavate.