There is one major problem with interfacing P-channel MOSFET to a microcontroller when switching [relatively high] voltage - when the control circuit closes, the switched voltage (i.e. 12, 60 or 80V) is applied to the microcontroller pin and it will be destroyed, because Netduino max pin voltage is less than 10V.
You have to use second N-channel MOSFET (or NPN BJT) placed between Netduino pin and P-channel MOSFET gate to control it. The proper circuit looks like this:
You can replace Q3 + R3 with N-channel MOSFET (use R3 as pull-down, connected between gate and ground to ensure safe 'off' state).
I would recommend you to get a few different transistors and try low voltage (3.3V - 5V) circuits first, switching simple loads like LED and evaluate the possible configurations. After you understand how they work, you can 'upgrade' to higher voltage and current. Random messing with wires without understanding the basics is not going to end well...