That's the only 16' TT Sunline made in 1981. Sunline went belly up in 2006, so you probably won't find much about your trailer.
1981 Sunline Price, 1981 Sunline Values & 1981 Sunline Specs | NADAguides
However, name and model don't tell you much about how to maintain the RV. What you see in a 31-year-old TT is what you get. The only thing that might be weird about your trailer is the tandam axles on a 16' RV trailer. Most 16' RVs had a single axle.
As to how to care for and replace appliances and other components, go to the website of the appliance or component manufacturer. The manual for my TT is one page long, with info only on the frame and insulation built in. But it includes a coupla dozen or so sheets from the manufacturers of the various components with specs and care for those components. Water heater, water pump, jonnie, furnace, axles, tires, AC, cooktop, oven, awning, "rubber" roof, etc.