You have to pull the entire burner out of the furnace. You might have to get a new burner gasket if the old one tears. This is a sealed combustion chamber since it is in a mobile home. Now once you have the burner out all you do is replace the thermocouple exactly like the old one is installed. Also check to make sure the pilot orifice is clean while you are into the thermocouple replacement.
If this is LP gas be VERY CAREFUL. Yes it seems like a lot of work just do not rush yourself and put everything back just like it was.
Take a good look at the burner. if the flame plate is burnt or rusted or in any way deformed you will have to replace that part also.
Mobile home furnace help can also be found here.
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