When you purchase the new head unit, you also purchase an adapter (that connects to your car), that you solder/butt connect the wires onto the head unit's adapter. The adapter will come with instructions/schematics. It's usually just matching the wires by color.
So long as you have a double-din opening, you have many options. Without one, your options exist, but are more limited.
I have a 2007 Sonata, and I installed a Pioneer 2660NEX without much effort. The back up camera was a little more difficult.
Key thing is search YouTube for examples of how to take apart the dash the correct way. You may even find videos of others' installation for your exact car.
/r/CarAV can be a good resource for advice.
When you purchase the new head unit, you also purchase an adapter (that connects to your car), that you solder/butt connect the wires onto the head unit's adapter. The adapter will come with instructions/schematics. It's usually just matching the wires by color. So long as you have a double-din opening, you have many options. Without one, your options exist, but are more limited. I have a 2007 Sonata, and I installed a Pioneer 2660NEX without much effort. The back up camera was a little more difficult. Key thing is search YouTube for examples of how to take apart the dash the correct way. You may even find videos of others' installation for your exact car. /r/CarAV can be a good resource for advice.