We were in the same boat. I wound up getting the make and model number off of every component; fridge, AC, furnace, etc and finding them online. There are user manual websites that sell downloads but I was able to find all mine for free. Good luck!
At the bottom of the Gulf Stream Owners Manuals page https://www.gulfstreamcoach.com/manuals is a section called Archive of Component Manuals. It says Under Construction but you might get lucky.