That would depend if you are looking for:
Not sure about the first, but for *new* equipment, the best place to find 'what fits', is at Crutchfield.com. Plug in the vehicle specifics and their system presents only the after-market equipment that is specifically compatible with the car.
Note: if you're looking for a new in-dash unit, there are converters for the dash panel that will allow you to install an after-market radio/cd.
See "Related Questions" below for more
First place I would check are the local auto salvage (aka junk) yards.
It is in the far back on the passenger side by the door.
For a 1999 Mercury Sable wagon : I believe you will find the six disc CD changer ( if equipped ) in the cargo area behind the panel for the storage compartment / service compartment on the right side
Any Cd changer will work long as it is installed right.
If you have a center console, that is where you will find it. If there is no center console it is in the trunk.
Yes, the cd-changer was an option - and found in the left rear corner of the trunk. See "Related Questions" below for more
According to the 1999 Mercury Sable Owner Guide : The 6 disc CD changer is in the trunk ( or if it is a wagon , the passenger side storage compartment in the cargo area )
The CD changer is in the center console of a 2000 Mercury Villager
According to the 2002 Mercury Sable Owner Guide : ( the 6 disc C.D. changer is either located in the center console , the trunk , or the right side of the cargo area , that would be for the wagon version )
I think the disc chamber is in the trunk. Centre hanging from the top at the edge.
The CD changer is located in the trunk - back, left-hand corner. The lid lifts up from the top and pivots towards you. Slide the cover to the right and push the button to eject the cartridge.
In the trunk, in the med compartment. It should be on the left hand side with a cross on it. You should find a cable in it that connects the CD changer