Unfortunately there is no such thing as a Sunline manual. When I bought my first trailer I too was surprised not to find a nice manual something like my truck, but then I realized the car companies produce hundreds of thousands of one unit while the trailer companies make hundreds or at most thousands. Sunline did have some photocopies of photocopies, or worse, in their 3 ring binder, but it's all fairly generic, much like the first couple of pages you get with a new fridge or stove. The two most useful pieces of info were the jack points and location of low point drains. Some, I believe, had a wiring diagram too. The whole rest of the manual consisted of appliance manufacturers' stuff like fridge and stove manuals.
Henry