For $10/day, you can park your entire RV in the Durango & Silverton NGRR parking lot and ride the train to Silverton. Then you take their bus back to Durango and get to see Animas Canyon on the train and the Million Dollar Highway on the bus. That way, you leave the driving to them and get to enjoy and photograph the spectacular scenery in both directions. Could save your sanity and your marriage as well!
The other suggestion would be to check with the La Plata County Fairgrounds about leaving your trailer there. They have a campground with electric/water hookups and may allow you to park a trailer temporarily. Of course, you could also spend the night there for $16.50 including hookups.
Personally, I wouldn't even THINK about leaving my trailer unhooked at the Durango Walmart, Home Depot, City Market, etc. And not because of theft, but because of the Durango police. Do you know how many people are looking for free parking every summer and fall morning in Durango before the trains leave? About 200,000 riders a year, on 4 trains a day, on the D&SNGRR. Plus non-train riding tourists--fishermen, whitewater rafters, campers, Jeep tours, etc. And almost all of that traffic is between Memorial Day and Labor Day.
"Retirement is the best job I ever had!"
2015 RAM 2500 4x4 crewcab 6.7L CTD; 2016 Rockwood Signature UltraLite 5th wheel