chevy429,
adding a cd changer to the 2001 focus is easy. I used to have one and I have the tape player radio on my desk right now. To add CD changer to this, you can either use the ford dealer installed units that work by using an FM modulator or you can use just about any cd changer that takes the 12-pin plug. I would go with one from a taurus, expedition or other vertical mount. The changers from these cars from 2000 up are the smaller clarion units. You did not mention if you have the 3, 4 or 5 door. The vertical mount* is the way to go if you have a hatch so that you may maintain most of your storage area. For the install, the 12-pin plug attaches to the "green" 12-pin receptacle in the back of the radio. The other 12-pin plug attaches to the changer. No additional lines are required to power this unit.
good luck
*there is a difference between the vertical and horizontal mount changers. For the vertical mounts, there is a spring that helps to stabilize the player. Horizontal mounts do not have this spring and cannot be adjusted without it.
