You CAN go over Red Mountain Pass from Ouray to Silverton and then Coal Bank and Molas between Silverton and Durango, however I would advise against it in any RV. Yes it can be done but it is not advised and most large trucks turn off at Ridgeway and use 62 to go via Telluride instead of Silverton. I lived in Durango and worked in Grand Junction and have pulled trailers and driven large trucks, over 550 but only because I had to get them to Silverton. AS mentioned there are narrow spots with no guard rail, switchbacks, and long steep grades.
BTW: I have driven through snow and ice on Red Mountain pass in August, so regardless of the weather in the valley look at the peaks to see what you will be driving into.
The rest of your route on I-70 and 160 is a easy and will not be a problem.