I would just skip straight to the radio, you can get a Metra 99-8231 Dash Kit, which will let you use any double din size radio. I recommend the Atoto f7 xe, which can be found for a bit under $200, and gives you wireless carplay/android auto. Lastly you need a Metra 70-1761 Receiver Wiring Harness, to connect to the car’s wiring.

Its a relatively simple process, and you can technically do it without any soldering.

I would grab an ECU from a scrapyard and start there, pennies on the dollar.

17% APR, absolutely abhorrent. A new car will not dig you out of your hole. Buy a used toyota for 5k, sell your 2022 20k dealer markup dodge charger, and work on paying down the loan.