Only one oft repeated don't around here:
DON'T use silicone-based caulk on the exterior. The fix for a leaky window or vent is to R&R with fresh butyl tape (or a fresh gasket in the case of fixed plexiglass windows).
DO check the tire dates and condition. More than 6-7 years is aged out, regardless of tread.
DO check the adjustment on your coupler before your first tow.
DO check the condition of the rubber torsion
axle. As you jack up one side of the trailer on the frame behind the
axle, the wheel should drop several inches. If it seems frozen in place, the rubber inside is hardened and the
axle is dead.
DO test your LP plumbing before using any of the LP appliances. A drop test (similar to the test they do in residential systems) is a great start.
DO inspect your
electrical system (or have someone knowledgable do it). In 36 years, no telling what someone may have done!
DO check the subfloor for soundness, especially inside benches and cabinets around the perimeter of the trailer.
And finally,
DO ask lots of questions.
DO start planning your first few trips. Some destinations require reservations well in advance. Close to home for the first trip is a good idea.
DO add personal touches to make it your own.
DO have tons of fun!
Congratulations, and happy camping!