If you are going to use autosteer at cm precision you should think about a rtk gps receiver.
This is a line up in gps starting with low precision.
At the GPS module you solder either 4 cables, or better a 4 pin 1.27mm connector to GND / Vcc / RX / TX. This GPS module runs at 3.3 to … V so the 3.7V battery is fine. The charger module is in between the GPS, the Bluetooth module and the battery. Between the Battery and the charger I put a 500mA fuse. You connect the charger to USB and the devices are powered and the battery charges. For communication BT and GPS are connected via RX/TX (crossed). The UART (RX/TX) is normaly activated in the UBlox, you don't have to do anything, the sentences it sends also fits to AgOpenGPS. If you need RTK the module may process it, but I don't know how, I don't use RTK at the moment.
Prices are only an estimation. They also have very different functions included.
Configer the UBlox with the U-Center programm for windows. You get it on the UBlox homepage The pictures show UCenter version 8.29. UCenter works with a USB and also with a Bluetooth connection, shown above.