If your car uses a DIN mount for the radio, it's generally easy to find a compatible aftermarket head unit. You'll likely have to get a wiring harness adapter,

If your car uses a DIN mount for the radio, it's generally easy to find a compatible aftermarket head unit. You'll likely have to get a wiring harness adapter, and doing a tidy job mating the two halves of that requires a bit of extremely basic soldering and the foresight to purchase some shrink tubing. The only downside to going this route is that most aftermarket head units look like they were designed by 17 year old young men to impress their peers. AIUI, If you don't have a DIN mount, it's usually possible to purchase an adapter to get the physical interface sorted. Aesthetically, it may be a crapshoot. The only cars I've done this on (because of a failing cd player) have had a DIN mount.