Lots of options and most of them will orient to how you use your RV because of power considerations. The simplest solution is to buy a new headunit with disc player and install. If you had one of those 1.5 DIN sized units, it can be replaced by a 1.0 DIN unit with an accessory fascia plate or bin. If your wires have been cut, you'll also need the pigtail that connects to your new headunit, if not included. These are the 12V choices.
If you always have 120V power available, you can buy a disc player and an amplifier and wire direct to the speaker wiring from your previous unit. When choosing an amplifier, get one that is compatible with 4 ohm speakers. The small digital "T-amps" are compatible with 4 ohm speakers and can also be run at 12v from battery or a walwart transformer.
My entertainment system is all 120V. I chose to do it that way because I have better components than 12V offers and my inverter is on while traveling or boondocking.