Are you looking for the circuit diagram and build everything yourself? down to component level? Sorry but I dont think you will suceed. And how about the firmware? where you gonna get the parts? how you gonna calibrate?
The best thing you can do is buy the GPS module, the antenna and stick a few wires in. The cost of it all will cost you the same to buy a complete combo unit.
http://www.garmin.com/products/gps15h/
Age 14?