I've performed all the maintenance and attended to whatever minor issues that have cropped up over the last 6 years on our TT without ever returning our rig to the dealership, although they have provided miscellaneous parts from time to time. Most items in your TT will have product manuals that indicate maintenance intervals including cleaning and trouble-shooting procedures. Checking exterior sealants and battery fluid levels/connections should be performed throughout the year with wheel bearings/brake operation inspected prior to the beginning of your camping season.
No reason you couldn't just haul your TT down to your preferred service center (that's what my neighbors do} but if you are handy with tools you could perform many of these tasks yourself with the satisfaction of knowing it was done to your specifications. Becoming familiar with your rig's major systems (electrical, plumbing, propane delivery, etc.) is paramount and will surely pay dividends in terms of your rig's overall longevity, durability, plus effectively reduce the amount of downtime over it's lifespan.
We've been pretty lucky with our current rig and have never experienced any significant issues while using our TT that couldn't be readily addressed and rectified, knowing how to use a multimeter (volt, amp, ohm measurements) greatly enhances the ability to diagnose AC/DC voltage issues that may occasionally arise as they can quickly ruin your trip and most times are relatively easy fixes. Just keep reading this informative forum as many of the most common issues with RV systems are posted and their solutions covered in detail providing insight for those attempting to remedy their own issues before relegating the repair to their preferred RV servicer. Happy Camping!!!