" I've read that pulling that front bushing, to install an Okie bushing can be a nightmare. How true is that?"
There shouldn't be a problem if you use the Bushing Puller

If clearance exceeds .010" the bushings and oil seal should be replaced. Check Note: Inspection step 1

Was the oil leak at the end of the retainer? Picture and HERE

You could have a wore ball housing or torque tube end. Look at slides 35 thru 46 GM film strip..

1954 Chevrolet 3105 Deluxe Panel Truck
w/Factory HYDRA-MATIC