You don't need to mess with the oil pan. Remove the transmission, clutch assembly, and flywheel and you'll have a clear shot at the rear main seal.
Do you have the OHV or SOHC engine? I think both are the same, but my experience is with the OHV engine only.
The old seal came out pretty easily using a small prybar, being careful not to damage the sealing surfaces. Others have used sheet metal screws threaded into the old seal and using this to pull it out. Clean up the sealing surfaces with some fine (000) steel wool. I think scotchbrite would work as well.
If you buy the Ford seal, it's a rubber type seal and comes with a repair sleeve. IMO if the crank surface looks OK, don't mess with the sleeve. I had to redo this job 3 times because of that damn sleeve - the previous owner had installed the sleeve upside down which I assumed was correct, so I did the same, which destroyed my seal twice.
The teflon sleeves are supposed to be more durable and forgiving of surface imperfections compared to the rubber ones. They must be installed dry though (no oil), upon first startup they coat the mating surface with a layer of teflon and this can only be done if the seal is dry. Even though I had to pry off an old repair sleeve which definitely did no favors to my crank surface, the teflon seal only weeps a little bit of oil, a small enough amount that its not measurable on the dipstick.
So - IMO - get the old seal out, clean up the mating surfaces, if the surfaces look good and feel smooth, get a teflon seal and put it in. If its gouged up, get a seal with the repair sleeve.
