No direct help. But it is a great plan to know how to access it. Most of the time when it fails is when your camping and you have not back up plan.
Sounds like you have an access door on the outside of the MH (very nice feature) If so, you need to remove the exhaust pipe on the door. Open the door, do your work. When complete, reverse the procedure, you may need some butyl tape to make weather tight.
There are some great Youtube videos on how to access the sail switch via an outside access panel.
Here is an OK link to open the outside access panel (3min 50 sec).