I think what you are referring to as a shop manual for the house portion, Winnebago refers to as a "parts manual" for your model home. This may or may not be available for your unit. It is a book completely listing all parts used to assemble the unit along with exploded drawings and part numbers. They also have electrical and plumbing schematics posted on the web for later models. Again, yours may be too old to be included on the web.
For something like your fridge - if you know the brand and model number you can go to Bryant RV
, scroll down the page to find your model and download the complete service manual. This is the manual the service techs use. Also on the same web site you can find the original service manuals. You may also find the manuals for your furnace and water heater here among others.
Chris Bryant runs an RV service center in Florida and had been kind enough to post the manuals on his web site. Wish I lived closer, bet he is a capable and honest service tech. If you have other manuals you are looking for, send him an email and he may be able to give you the web location to find them. He kindly helped me out that way on an uncommon item.
Hope at least some of this information is helpful.