When R&Ring the flexdisc; if the original relation between drive shaft & differential are maintained, is it a simple change out or are there difficulties associated with preventing driveshaft vibration?

When R&Ring the 2 rear differential bushings, what size is the hex drive? With a jack supporting the diff, will the bolts come straight out? There is only about 3 inches between the bolts and the gas tank on a wagon. Does the gas tank have to be removed?

Are there any special concerns or difficulties when doing these 2 R&Rs?

Bob