I have ridden in the Stampede parade in Calgary with Sam Elliot, and you won't find a nicer, honest, and genuine guy in the film/tv business IMO. He's been the Marshall of the parade several times over the years. We've had a good talk for about 15 mins about various single action revolvers and about Wild Bill Hickock and other infamous gunfighters of the west. He always took the time to talk with anyone who wanted to speak with him, like I said, a very genuine type of guy.
OP, I hope you have a great time being an extra. I did it once long ago on the film Legends of the Fall, being a WW1 soldier during the scenes they shot regarding the three sons being in Europe with the Canadian army. It was a blast, lasted several weeks while they did principal photography and shooting and such, plus Brad Pitt long before he was really famous responded to one of our guys notes inviting him out to hit the town with our group. He wanted to drive around and look at local older architecture instead of bar hop, pretty interesting guy too back then.