I would say its worth the drive, they have some very historic guns and unique one off test guns as well as a lot of other interesting things including around 10-15 tanks. You can get on post with no problem, come in through the i-185 gate and stop at the visitor center and tell them where you are going they will give you a temp pass to get on post for the day make sure to have you insurance, drivers license and registration and to carry it all into the building to get the temp pass. They are currently working on a new museum site that can be accessed from off post, it is going to be enormous and include a company "street" from the world war 2 period however this won't be open for at least another year. Right now they have a lot of stuff they don't have room to display. You could easily spend 2-3 hours looking through the museum.