You'll have a great time. I went in the summer of '01 and had a blast. The National Parks Service and NRHS go out of their way to make sure its a week to remember. You go to many spots in the Steamtown shops that are off limits to the public, our class got to crawl through the firebox (unlit, thankfully) of a steam engine, and go on, under, over, and inside the locomotive to find out what makes it tick. You usually get bused one day to a big CN yard in NY state, complete with a tour. There is a big big emphasis on RR safety, not just that day but the entire week. You learn how to change brake shoes, how to replace broken coupler heads, spend a morning with Steamtown's train crews reviewing the NORAC operating rules, and in the afternoon learn radio rules and hand signals. Then, you go out to the real thing and with the conductor, make hitches, put air hoses together, and put hand brakes on.
At some point during the week the 1205th US Army Railroad Batallion comes and visits to tell you a little about their unit, and a few railroaders come and explain what its like working for a railroad. If the RR is nice enough to give me the day off, I try and visit with Charlie Albanetti, former editor of "The Teen Track" from Railpace. We are both graduates of the program and still talk to the group leaders and former campers to this day.
Hope to see ya there,