Go to Crutchfield.com. They have harness adapters and faceplates for almost any vehicle. I've used them for years, they're great!!
The 2001 Mercury Sable does come with a CD player. If the car does not have a CD player in it, an install kit can be purchased to install a CD player.
Most Cd players can be installed into your car within 1-2hours and basic knowledge of tools.
You can't install a CD player into an older model car because it doesn't have the right wires.
car goes vroom
Normally in the modern cars there is no necessity to install the CD player, as they are already accompanied in the car radio. Otherwise the user has to follow the instruction manual.
I really doubt there is a kit to install a CD player in that car, you will have to install it on your own somehow.
Get a new CD player
It depends on if you are mechincally incline to do it. It could be an all day project.
To install an aftermarket CD player in a Toyota Corolla a new wire harness is needed that corresponds with the replacement player. The old radio needs to be removed and the harness will need to connect to the cabin harness. Then the new CD player can be installed.
Google the model car and the wire diagram follow cd player diagram and fix wires together
Park your car in the "Shady" side of town (usually the area with highest number of black-people) They will remove it for you. Then you can install your new CD player. Its really that easy. They will do the work for you.
Follow the Youtube video.