My truck is a 1993 Toyota V6 4x4 with 199k miles.  The clutch was
replaced at 119k miles when other engine work was being since the
transmission was already pulled back.  At the time, the tech told me
that the new clutch should last even longer than the original one.

Well, here I am 80k miles later and I don't know if I have clutch
problems or what.  Sometimes when I put the truck into 1st gear, it
will pop out of gear from a cold start (if I shift into 2nd gear before
going into 1st, this never happens).  I've been driving this truck for
so long that it's hard to remember what it used to drive like, but I
swear it's losing power, especially going uphill.  It got new plugs and
points recently, which didn't improve the performance at all.

I recently tried pulling an empty dual axle trailer and the truck drove
jerkily.  I assumed it was the trailer, but maybe it was the clutch?

What's the definitive test to find out if my clutch needs to be
replaced?

Thanks.

--MATT