From what can be gathered about the Kindle Fire, the USB it slave only; not a host port. meaning it can only be plugged into a computer and used for the dev bridge, and one big flash drive. And not big as in space, big as in physical size.
I hope I'm wrong, because I want to be able to plug in a USB keyboard and mouse. However if I am wrong, your GPS receiver will still not work, because of the lack of drivers for the device, and lack of GPS software w/maps. I doubt Amazon will allow google maps and nav on the device, and even if it did, you would still need an active Internet connection for it to work.
I'm sorry to be the barrier of bad news, but I don't think this will be possible. However, this is still an unreleased device, I COULD be wrong, but I doubt it.