That looks like a "double DIN" size or possibly a "1 1/2 DIN". I believe it's a head unit, meaning that the electronics are behind the screen. On some units there is a separate "core" unit which is a computer installed in an upper cabinet separate of your screen.
Some obvious places to shop for a replacement is Crutchfield.com OR to take the RV to any good Auto Sound installer shop near you.
You said you don't want GPS, but what about backup and side monitors, DVD, Bluetooth, Sirius/XM radio and other features. You'll need to talk to a specialist to get everything you want. Crutchfield.com will help you a lot over the phone, or if you go to a shop they will offer what they sell.
2017 Winnebago Adventurer 37F
2016 Lincoln MKX Toad