I think that responders to your request for help all assume that you are coming from the UK. So I would assume that driving on the "wrong side" of the road is best started from a simple place, not a huge city, and probably best started after a night's sleep and after a bit of adjustment to the time change. So here is my idea for an easy start. Fly into Denver, take the RTD train from the airport to Union Station and spend the night in a downtown hotel. The next morning board the Amtrak train to Grand Junction and enjoy some fabulous scenery climbing over the Front Range of the Rockies, and cruising through the canyon country.
Here are some scenes you would never see from the road
The train travels many miles thru Red Rock country
If you book the Clarion Inn in Grand Junction, they will pick you up at the Amtrak station, and take you to the rental car counter at the adjacent airport in the morning. If you book a one-way rental car for return to Denver, you have a world of wonderful options available. You could drive directly south to Montrose (90 minutes) with the option of a side trip to the nearby Black Canyon of the Gunnison National Park and/or visit engine 278 at Cimarron (the one-time narrow gauge exit from the Black Canyon). Then continue to Silverton and the first encounter with the narrow gauge ( 3 hours from Grand Junction, driving straight, or a bit longer if you want to enjoy the fabulous scenery while crossing 11,200 ft Red Mountain Pass. Then Durango, Chama and the Cumbres & Toltec celebrations.
If you want to take it a bit slower on your first driving day, we would most likely be able to put you up for the night at our house at Ridgway (the view from our house today, a bit greener in August)