Have a great time!

On my first trip to the C&TSRR, I was leary of riding a bus so I went from Chama to Osier and back and regretted it for a full year until I could come back to see the other "half" of the line. Both parts are spectacular and memorable in their own way; try to see all 64 miles while you are there.
My favorite trip is to start on the train in Antonito in the morning and head west to Chama. I like the Antonito end in the morning. It's a bit cooler and there is usually more wildlife to see. Since you are staying in Chama, this means you will catch a bus in the morning to Antonito which should have a Docent on board to give you an introduction to the RR and the history.
Much of the scenery will be above and below you while you are on the train. The best place to fully experience the panoramas, gorges, and spires is from the open gondola. Spend as much time there as you can. The gondola is available to all passengers once the conductor has been through the train checking tickets.
The C&TSRR is more than a pretty ride and the fruits of many hours of historic preservation are available for viewing, particularly in the yards where, with yard tour map in hand, you can explore and take a get your hands dirty approach to RR history. If there is an eastbound train the day you are exploring(by my understanding, from July 2 through August 14 eastbound departures are scheduled Sat, Sun, Mon, Tues, and Thurs), you will have to chance to see the locomotive serviced in the yard and then chase the train up the 4% grade to Cumbres pass. If you do, stick around after the train passes the third grade crossing and you will shortly see the engine round Windy Point, 300 vertical feet above you. You should still have plenty of time to drive up to Cumbres and catch the train there as it stops for water and, hopefully, cuts off the helper.
There are ongoing preservation and archeological efforts at Cumbres Pass which you can see while you are there. You can get a walking tour brochure of Cumbres Pass at either depot or from a Docent.
Enjoy the experience and take fair warning: it is addictive!