Wow, that doesn't sound good. I don't have direct experience with my Jeep, but when I was a kid something similar happened to our Dodge Caravan on a family vacation to the beach. My dad always had a manual gearbox, even in the minivan! As I remember, he lost fifth gear first, but it wasn't long before other gears began going too. He was able to coast into a town that has a Midas garage. We were stuck at the Midas sitting on our suitcases for about 8 hours before my Grandad could get there to pick us up. Moral of the story: get this fixed soon, even if it seems like you're only missing one gear, because you never know how long the tranny will hold together.
Maybe someone else has a better answer.
