Highly recommend going to
Crutchfield.com and pick out something that suits your needs. These people are amazing, and fantastic to deal with.
The units come with excellent instructions, very clear and concise.
The unit will be a lot smaller than the big ugly things they stick in RVs at the factory.
I have done 2 of these in the past 2 TTs I've had. One of them I got a piece of black aluminum flat stock and custom fabricated a face plate to cover the open area left by the oversize factory unit. I cut a hole to fit the new unit. I went with double Din as opposed to single. More screen space available on the new one. Because the unit goes into a cabinet, it is easy to mount some wood inside to fasten the mounting brackets to. I used a small screw on each corner of my fabricated face plate to hold it in place.
Second unit, same story but I made a replacement face plate from a thin piece of wood paneling, available anywhere. I bought a tiny can of wood stain that matched my existing interior color, then clear coated it with matt finish spray varathene. And again, 4 screws, one in each corner to hold it in place. Screw heads can be disguised with a dab of paint to match the color.
Wiring? Piece of cake. The factory units had tags indicating the purpose of each wire. The new unit, clearly marked. Cut the wires one at a time and solder, shrink tube them together. A few small zip ties and you're good to go. Because there is no accessory position wiring in my TTs, I tied them both to +12V. You could put a switch in to mimic the key on/off action, unless your HR has that built in. Depends on what you want.