There is one thing that I have learned over the 5 years we have had a trailer (2 trailers during that time). Aside from the black tank business and the water systems in general (which are important)... THE most important thing you can do is keep the water OUT of your trailer. Roof maintenance and caulk inspections around all fixtures sticking out the sides of the trailer are a must. Black tanks and plumbing can be replaced (in your driveway if you are handy), but once you've allowed water to inject itself into the walls or ceiling or floors, you are in a whole bigger world of problems.
Just my .02.
Last advice...... like others have said, take this all in stride. The STACK of manuals and paperwork that all seem to say "if you don't do this or that we might come and take your first-born!" can be overwhelming. Once you have owned it for a year and have been out in it 5 or 6 times, you will be a pro without thinking too much about!