It's not hard but will take a hour or two of fiddling around the first time you do it. Dont' start when you're in a rush. The motor and rail assembly were one unit on my replacement.
Remove the door panel and all wire connections. Disconnect the power door lock mechanism. Disconnect the door opener mechanism from the inside of the door lever (a small clip holds it on). For the manual door lock, free the lever from the "PIVOT POINT" near the rear of the door. You will not need to totaly remove it. Next, remove the large silver mounting plate in the door. Once unbolted, it can be removed by tilting it out at the top.
With the window part way up you will be able to see and access(through two circular openings) the 2 nuts which hold the window to the rail mechanism. MARK WHERE THE WINDOW IS before loosening. (I used a small felt pen.) Set the window aside. You can do this without removing the window from the door, just set it out of the way inside the door.
Remove the 2 bolts in the top and 2 in the bottom of the door which connect to the window rail. Remove the rail, which has the motor on it. Replacement is the reverse procedure.