Are there any Sketches that Arduino has that could be used to operate a remote controlled planes mechanical functions?
Check out the ArduIMU project (http://store.diydrones.com/ArduIMU_V3_p/kt-arduimu-30.htm
) such as http://code.google.com/p/ardu-imu/
There are also (many) others.
Also does Arduino manufacture boards that can be waterproofed so they can operate in wet weather?
Plug in all things you need plugged in. Put a smearing of ScotchKote or acrylic conformal coating over it. Done!
Or use a weatherproofed enclosure, like an OtterBox (http://www.adafruit.com/products/340