the carrier bearing shims arent that big of a deal to install... you just unbolt the bearing mount and put it in. then bolt it back up. they may include longer bolts in the kit. They just correct the driveline angle offset produced when you raise the rear end into the frame to lower the truck.
Same with the rear end shims. just loosen up the u-bolts and slip them in. they should have a hole in them that goes over the alignment peg in the spring pack. it turns the rearend and does the same thing... it corrects the change in driveline geometry produced by lowering the truck. they are cheap little parts that can save you some cash later changing u-jounts.

- If you were going to do the job, I would just put the shims in the rearend. the ones in the carrier bearing are not needed unless you go farther with the drop. Thats about the best advice I would give.