Why do you need windows? An 8-bit (such as the 18F8722 found in the FRC controller) device is completely capable of handling a GPS device (most have baud rates around 2400 to 9600), multiple supplementary sensors for between-gps-sample navigation (GPS usually updates at or around ~1Hz) and some pretty fancy navigation stuff no problem.
No bluetooth or USB required. The USB pharos module listed in a previous post is, at it's heart, an RS-232 device. There's just an adapter on it's output. If I remember right, pharos GPS devices are 2400 8-N-1 as are many other GPS devices.
It also seems Spark Fun has a new GPS reciever that's pretty gosh darn cool... it claims a 5Hz update, the fastest I've ever seen. (
link to page)
As far as the serial data goes, using Kevin's serial driver would work fine, but it wouldn't be too difficult to write your own either. You'd have to write the actual parser yourself, but NMEA isn't that confusing to look at and doesn't take long to figure out. It has no checksum (if I remember right) so there isn't a whole lot of logic needed to securely recieve data from the sensor.
This sounds like a GREAT project... I wish I could help!
By the way... if you don't mind my asking... what does this thing look like? Big knobby tires? What kind of implement are you going to use? If you had a big fenced in area (for safety) it would be fun to take a 12v weed wacker and mount it on your machine so it could cut grass.
Awesome! Good luck!
-q
EDIT/ps: As one of your supplementary sensors, I suggest using a really good gyro. The analog devices ones are really good, but can drift with temperature and off-planar rotation (such as if your machine was on a banked hill tilling earth or something). You might consider using a
Gyration 5 DOF motion sensing part.