If your TFI Module fails (likely leaving you stranded on a rainy day), the quick and dirty replacement of same may be a short-term fix of the SYMPTOM, rather than the CAUSE of the problem. The smart thing to do is replace the PIP (a likely cause of a TFI failure) and the TFI together (unless you are stranded by the side of the road and just need to get home by replacing the TFI. Another solution is to replace the distributor with a rebuilt one AND a new TFI. Rebuilts are available from FORD under the Motorcraft name and come with a life warranty. They come with new bushings, PIP, and BRASS GEAR.
The TFI (DY-425) is a grey box attached to the side of the distributor with a black quick connector bringing in the electrical connection. It can be replaced in ten minutes without removing the distributor, but removal absolutely requires a special tool (KD Tools #3197 or Lisle #64650) to remove the two small hex head bolts. The PIP (DU-30-C) is located under the rotor and requires removal of the distributor and subsequent removal of the attached TFI Module (one more reason why it makes sense to replace both items at the same time).
Removal of the distributor is accomplished by removing the hold-down bolt and arm completely and then pulling the distributor straight up. However, before doing this, mark (with White-out) the location of the distributor housing to the power steering pump and the shaft cap to the distributor housing. Make note (and mark the final position with moreWhite-out) of how the cap turns clockwise as the distributor is pulled upwards (this will be the starting placement when re-inserting).
To get the old PIP out (and the new one in), the distributor shaft must be completely removed. To do so requires removal of the distributor gear, which is pinned and pressed on. Before removal, scribe a line on the gear and shaft to make sure they are returned to the same place. Removal of the pin is easily accomplished with a 1/8" drift. Removal of the gear is easily removed if you have a press or can take the part to a machine shop. Barring that, it can be removed by holding the outer shaft in a (well padded) vise and hammering the shaft out. BEWARE! Doing this will very likely "mushroom" the end (either one) of the shaft and you risk destroying the part! A file may come in handy to "un-mushroom" your handy-work.
With everything disassembled, replacing the PIP and TFI is child's play. A 5.5mm socket/ratchet and the special tool mentioned above is all that's required. Five minutes and you're done ...except now that damn gear has to go back on. A good pair of eyes will be needed to align the holes for the gear pin - if it doesn't go in fairly easy, you've got things misaligned. Try not to break anything :-).
Be sure to re-set the timing once you've got the distributor dropped back in. If you were accurate with your White-out, you shouldn't be off by more than a degree or two.