Should be like any other M4 AEG. Mechbox.com has a bunch of vids (although other parts of the SCAR are different).
1. Take off motor/grip plate
2. remove wires from motor
3. remove motor
4. remove screws holding grip to mechbox
5. swap grip
reverse to reinstall everything...then readjust the motor.
If you're not 100% on any of that...research a bit more (i.e. mechbox.com...ASC search for Motor Height Adjustment...etc...)