I started looking in the service manual of my 1979 Catalina to see how to replace the rear main seal. The procedure says the transmission does not need to be removed. There are two parts to the seal, the lower seal sits inside the rear main bearing, which is accessed through the oil pan after having removed the pan and pump. The upper seal seal is above the crankshaft, but apparently accessible with the crank in and out of the block. The seals themselves are a pair of rope-like pieces for the top and bottom. How difficult of a job is it to replace these style seals as a DIY-er? Would the relative ease of access from below make it much cheaper to have a pro do it, since I've never messed with these before? I thought about putting a new oil pump in there as well whenever I decide to get the seals fixed, since that comes out for the seal replacement procedure and it's 42 years old as it is.