The guibos look pretty visibly dry and cracked Mike, if you are doing the center carrier bearing I'd do both the guibos too.
Cheapest I've found is here:
BMW X5 Driveshaft Parts | FCP Euro
Either way its about $260 for all 3 parts, and any hardware to reattach it, but since those guibos take a lot of the vibration out of driving it really should smoothen it out.