First off I would say dress for comfort. You will be sitting for about ten hours with a two hour break for dinner. The are long enough breaks between presentations to attend to calls of nature. You may want to bring something to place on your seat while you are on such a mission. If the weather is warm, like predicted, it is probable that the temperature in the theater will get hot by the end of the night. Dress accordingly. If you collect railroadiana bring lots of money. The theater doesn't open until about an hour before the show starts so you will find people starting to line up about an hour before they open it up...a couple of hours before showtime. Unless you're intent on getting a specific seat or something in the center of the seating area this probably isn't something you need to do. Almost any seat is fine as far as I'm concerned.

I hope this helps. I'm sure you'll get lots more suggestions and ideas. You WILL enjoy the experience.