I'd tend to agree. I'm not really sure EXACTLY what they are calling a "carrier bearing", but a little research states it's basically what aligns your driveshaft with your transmission and diffy.

That being said, AutoZone lists one (not sure if it is the one your dealer is talking about) for something like $25. I would think you could find one for a Trooper somewhere as well (assuming they are the same part number).