Hello Bob,
There is a telescoping section built in the drive shaft. You will see one large lock nut on the drive shaft just in front of the carrier. I think the two sizes are 46mm and 42mm. Some large adjustable wrenches can work if you do not have the special tools. Once the nut is loosened, the drive shaft will move back about 1 1/2". After moving the drive shaft back you can pop the aluminum centering flange off the end of the drive shaft, this will allow the drive shaft out of the way so your damaged flex disc can be replaced. Check for damaged bolts, damaged holes in the drive shaft flange, damaged holes in the transmission flange, damage to the aluminum centering flange, and check to make sure the rear slotted nut in the transmission flange is tight and locked in place (important). New locking nuts are also a good idea. Make sure the two different bolt lengths and the washers are in the correct location. (check the tech manual under "drive shaft flex disc"