This kind of stuff isn't really hard. So much of the real work for stuff like this is already done now that it's more akin to building the old Radio Shack projects when we were kids back in the olden days.

You pretty much grab stuff off a shelf and bolt it together and wire it up and play with it.

The Raspberry Pi has a "Getting Started with Python Programming" lesson that is so well done that anyone who can read and write and do basic math will understand how code works. From there you can pretty much jump right into using example code for things like this compass I'm fooling with now.

The Raspberry Pi cost about $35 + shipping, and you can get a nice GPS receiver to wire into it for about $35-$50 or more. I'm not sure what kind of software is out there that will run on the RPi though. I found one project that's making something pretty close to commercial GPS software, but my Garmin doesn't let me access the data I need to use it and I haven't tried installing on a RPi yet. I have my doubts that it will run very well on one, but it's worth trying cause it's free