I have changed the gears in my rear end housing on my 1969 Plymouth 8 3/4" from 3.23 to 3.55. I now have to change the speedometer gear in my 833 4 speed transmission. The transmission is in the car unfortunately, not on the bench.
1. Can anyone give me an idea of the "level of difficulty" I am in for and anything special I need to be aware of?
2. After removing the bolt from the "bracket" or "tang" that presses against the pinion gear adapter, does the adapter and speedometer pinion gear just pull out?
3. When I am ready to reinstall, do I slide the pinion gear shaft into the adapter and then install everything back in place in the transmission as one unit or do I install the speedometer gear in the transmission first and slide the adapter over the speedometer pinion shaft and press everything into place?
4. Should I replace the adapter pinion shaft seal even if it is not leaking?

I appreciate any help or advice from those "out there" that have done this before. Thank you.