Howdy from Texas
Congratulations on your SS Agile. That's what we have and we specifically wanted that model because of the length. I agree with Mike. Spend a lot of time in your driveway learning what you can before you hit the road. Read the manuals for both the Mercedes and Roadtrek and take notes. We've had ours for almost 2 years and we think we understand MOSTLY everything! If you have never driven a Mercedes before, remember when you start the engine, wait a few seconds for the glow plug light to go off. Remember to buy DEF fluid and keep that topped off.
Learn how to fill and dump your tanks. It's pretty easy with the maserator. We flush the black water first and then the gray water which helps rinse the hose. You can continue to run water into the sink to keep flushing. Personally, we put TP in the garbage rather than the toilet.
We bought Reflectix and use it in the windows. It keeps you warm in the winter as well as cooling the interior now. Just cut it to the sizes you need. When we're parked, we find that with the windows open and the fan going, it stays pretty cool, but we are in Northern CA, not Texas.
I could write several pages here but I think once you do your "driveway"run, come back here with specific questions and we will be happy to help.
If you are on Facebook, there is a Roadtrek group where you can learn a lot and ask questions. Have fun!