Hello Patdf, good luck with this. Take your time, and don't use excessive force, and you should be OK. I have never had to change any of these needle bearings before, but it is doable. The thrust load from the pinion gear is taken by two large washers between the pinion gear and the inside of the upper housing. So, the bearings are just for radial thrust. Clean the bejesus out of the upper housing, you are looking for any kind of a shoulder or register that will keep you from pushing the bearings out from that side. If you have access to a press, that would be the best. Otherwise, a sturdy table, wood blocks to support the housing, and a steady arm with a hammer should work. Find a drift or socket that is a hair smaller than the bore the bearings sit in. It would be a really good idea to support the casting with a socket or piece of pipe a little larger than there bore the bearings sit in. Cracking the aluminum housing would really suck rocks...Go slow, and you should be fine.
Install the new bearings the same way. Me, I would add a dab of grease to each bearing, just because.
I totally agree with JDBrian. Using digital or dial calipers, or a depth gauge, find out how deep the bearings are positioned in the housing, then duplicate that upon reinstallation.
Good Luck! and we want pictures of how this turns out!:thThumbsU
Seth K. Pyle