Tim,
Yep it needs replacing, and its the whole unit probably (only very few can or are worth replacing just the bearings).
Shimano xt external are about £30 and worth it. Hope look fancy and have similar bearings, £100 one is probably ceramic bearings which last a little longer.
Tool is £10 and its an incredibly simple job to replace.
Give me a shout if you need a hand.
Gaz