Since we don't know where you you haven't been before, it's hard to guess where you might like to go and what you might like to do. Do you have a family? If so, what are the ages of your kids? What do they like to do (besides play video games and text!)?
A somewhat direct route for you to get some altitude (cooler weather) and scenery relatively quickly would be to head directly through Lubbock and up to Santa Fe. Then you could take US 285 to Buena Vista, US 24 to Leadville. From there, take CO 91 to I-70 to CO 9 at Silverthorne to US 40 and over Muddy Pass to CO 14 to Walden or Rabbit Ears Pass to Steamboat Springs. This route will take you through the San Luis Valley (and Great Sand Dunes NP) and past the Collegiate Range (the highest peaks in the Rocky Mountains), You will have several relatively easy mountain passes (Poncha, Fremont, Muddy-Rabbit Ears), but they should be little problem with your 5th wheel.
From Walden or Steamboat, you can head due north to Wyoming and several routes that will get you into Montana without going through Yellowstone. Take a look at my blog of Colorado's mountain US highways
HERE.