2015 is a far cry from 1980. I would NOT simply mosey over to the Cheyenne Heritage shops! For one thing, there is an unbelievable amount of attention focused there from the railfan community because of the Big Boy project. I would bet they get somebody knocking on their door nearly every day, "I wanna see the Big Boy!". For that alone I would not expect the red carpet to be rolled out, but also security in general is likely ramped-up.
Additionally, there have been several changes in administration of the program in those 25 years. While I'm not saying that the current staff is unfriendly or unwelcoming, they are under a lot of pressure with the Big Boy restoration, and it also has to be mentioned there is some unhappiness in the community close to the program about decisions made to facilitate the project. So they may be on edge. I personally wouldn't push it, not right now.