I also think that 60 hours is a bit short.
You may need some accelerometers. The GPS response is slow and so you may have the vehicle in an unrecoverable dive before the GPS notices.
I see the steps as:-
You need a microcontroller, so find out how to program those if you don't already know.
Connect some sort of display or readout to the microcontroller so that you can see what is going on. Test that.
You need to find a GPS receiver. We use the Haicom HI- 204III-PSII. I recommend using RS232 not USB. Connect the GPS receiver to the microcontroller. Program the microcontroller to send the something from the GPS to the display and check that you get sense out of it.
Do the same with the accelerometers.
Wire the microcontroller to the servos, and check that you can drive them over all the range you need.
Write some code to keep the vehicle level and see if that works. Then write code for all the other movements. Then use the GPS readings to alter the set points for the heading, roll, rate of climb etc.
That looks like what you need to do.
Have a dustpan and brush ready for mistakes!