Things to consider are whether it's really a complete set and condition of the film (which I believe is black and white, at least for the service ones) and the records. They usually got played only a few times at the dealership but bad storage ruins this sort of fragile stuff pretty easily. I don't think that the 1959s are on nitrate. (The oldest films date to the Twenties or Thirties, are nitrate and need to be kept in cool, dry storage. To display the nitrate ones, have a fire extinguisher at hand or convert them to a more stable medium.)
If I recall, there are ten to twelve sales training films and at least as many service training films for 1959. Maybe Yann's web site lists them. Don't confuse the sales and the service ones. The service ones generally bring less money. Very often, collections are a hodgepodge of sales and service.
The projector need not be equipped with a phonograph, but you'd need a phonograph to play them with sound. It can be a separate unit. The projector changed over time. In the 1930s there was no record; the training message was printed on the film, as in a silent movie. Yes, Dukane made a combo projector/phonograph. I saw one on eBay just the other day. I expect that GM arranged for a particular projector to be supplied with these films but I don't know which one it was for the late 1950s.
I bought one month's Cadillac sales training for 1959 a few years ago on eBay and paid about $100 for film and record in good shape and original packaging. So, maybe up to $1,500 if it's a complete, mint set of Salescraft films and records for 1959. About the same for the 1960 set, I imagine.