My I&T manual shows two bearings on each bull pinion shaft and two bearings on each stub axle shaft for a total of eight bearings and a bit of heavy work to get them all replaced. Hope you have a "cherry picker" in your shop or a chain hoist. those axle housings look HEAVY! Doesen't look too tough, just a lot of heavy parts to remove and probably a dirty job.
The price sounds right though.