I used to work at the museum but that was over 6 years ago, the firm I worked for had the maintainance contract for the buildings.
I used to watch and "spot" the old steam trains as I lived only half a mile away form the main east coast line, and traveled on some of them but it was a treat if you got on one of the new diesels as they were much cleaner?
If you go to the museum in a car it's about £10 to park they have a web site you can check, not sure how much the other car parks are but the park & ride are free but you have to pay on the bus?