It's entirely possible to do this job. Obviously there were 5-speed cars built right up to the end of production. You need the transmission itself, the easiest setup being an M47 (1987-up) true 5-speed transmission. You need a hole in the top of the bell housing for the crank sensor. An early one can be used if you break out the casting for the hole. A 1989 or newer unit will have the hole machined out.
The other items you need are as follows:
driveshaft from a manual transmission car
rear transmission rubber mount
clutch cable
clutch pedal + parts for under dash
brake pedal from the MT car
flywheel with the right number of holes: 40 holes or 57? Same as
your present flywheel has.
clutch kit: pressure plate, disk, TO bearing
pilot bearing for the end of the crank
probably figure on replacing the rear main oil seal while you're in there.
Figure on an 8-10 hour job for the home mechanic. Less if you've got a good trans jack and a real lift or a way to get the car up off the ground more.
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Rob Bareiss, New London CT ::: 86 244DL, 87 244DL, 88 744GLE: 625K total