All the bearings, gasket and seals add up to about $100. You'll need a torque wrench that measures over 200 foot pounds, the output flange holder to remove the nut, the flange puller, propane torch, and precision measuring tools to check bearing depth. I spent around $300 just on the measuring tools, though I've heard of using plastigage or other squishable material that can then be measured to determine the free space between bearings and cover.
Just guessing, I'm thinking about $500.
I forgot about the bearings - you'll need pullers to remove them. I use a 20ton press and have special pullers that can grab the bearing even though there isn't much purchase available. Maybe you could have a shop with that equipment do that for you.
The job seems hard the first several times, but once the obstacles are understood (like any task) it gets easier and easier. I'm sure brain surgery seems pretty simple to a brain surgeon. Seriously - it's a job to be taken carefully and methodically. And if it doesn't feel right when it's all back together, be willing to tear back into it.
