[tjsblazer]

Assuming your truck is still stock the front axle is a Dana 44 and the Rear is a GM Truck 12 bolt.

To do the bearings on the front, you need to disassemble the locking hubs then loosen off 2 nuts / locking washer that set the pre-load on the outer bearing. The hub / rotor assembly should then slide off of the spindle. From there you can replace inner and outer bearings and the inner bearing seal. Once your that far you might as well do the spindle bearing and seal and ball joints too unless they are recently new. You have it tore down to the knuckles by then any way. If there isn't any fluid leaks noticeable coming out the end of the axle tubes your good to go. If there is, it is sealed up at the diff so you have to pull axles and get in to the front pot to replace those seals.
There is info on this in the Service manual but I found information and exploded views on the Dana Spicer website more helpful.

As far as the Rear. The rear axles need to be slid out of the tubes after you pull out the C-clips. You can then replace the bearings and seal in the outer end of the axle tubes. A lot easier tear down compared to the front. This axle was used prolifically by GM though the 70's. Most any truck service manual would have information on this.

Probably can Google both and find service information posted on line also. You tube videos too.

My memory is terrible and I can't remember exactly what all this costs even though I just did mine in the spring but for all the bearings and seals front and back and front ball joints describe above I think you should be in the $200-250 range in parts.

Like I said before, you can do a lot without pulling off the tub unless you have a lot of metal work to do you can't get at. Doesn't sound like that is the case. The bodies do flex a lot once off the frame even with good metal and getting Doors fitting right is likely where the most time is spent.