Sounds like a half-shaft alright, but I suppose there are bearings down
there too.  Have you gotten under the car to inspect the axle boots yet?
More than likely, if a joint is failing, you will see a defect in a
half-shaft boot.  Possibly notice grease from the boot has been flung about
as well.  Half shaft will, or at least should have a boot on each end.  If
it's already started clunking, I'm not sure I would trust regreasing and
putting a new boot back onto the shaft.  At NAPA I usually pay somewhere in
the order of $130 for a reman half-shaft, then get somewhere in the
neighborhood of a $60 core charge back when I give them my old one.  New
one, not a reman I bought for my impreza came in around $80, so I didn't
bother with reman.

Also, there are shops that do nothing but rebuild/remanufacture half-shafts.
If you have a hard to find parts for car such as an XT-6, it may be more
efficient to take your shaft to a rebuilder shop and have them bring it back
to spec, right on the spot.

Do the work yourself, and you're obviously just out your time and cost of
the shaft.  I would think a garage could whip it out in an hour or so, if
they aren't too pokey, but maybe I'm low balling it a bit?  When I need to,
I usually seek out independants that let me bring my own parts for them to
install.  I know I take plenty longer than an hour when I change out a
half-shaft, but not having a lift or anything else to get me off of my back,
I take my time.

~Brian