rack boot logic

["Lewis Schnaper." <lewis@ukpik.com>]

Good morning.  

I bought a very clean and well-maintained 92 V-8 in California a couple
of months ago with about 75,000 miles on it.  When I got it home to
Anchorage the Audi-enthusiast shop here confirmed that the car was is
good shape except for one strange thing.  The steering rack boot is torn
on one side near the bolts, the bolt-tabs show that they've been bent
back, and one cover where the steering arm goes through the chassis (you
can probably tell that I'm describing this second-hand) is missing.  The
dealer that I bought the car from and who changed the rear main seal
said that he wasn't aware of any rack work that had been done.  

So I ordered up a new boot for all of $32, but now I'm having second
thoughts about paying for almost a day of shop time (maybe 7 hours at
$65 -- $455)  to replace it.  

Here's the logic the way I see it:
--First, there's no way to know whether this is the original or a
replacement (new or rebuilt) rack.  It's not leaking and my impression
from the list is that this isn't an item that should need replacement at
this mileage. I can't come up with a reason that it should have been
removed unless it was replaced, but it makes no sense that anyone who
would remove it would leave a torn boot.
--If I replace the boot I'm paying around $500 to maintain the status
quo. 
--If I leave it as it is (but replacing the outside arm cover) the worst
that can happen is that sometime in the future (maybe far in the future,
I don't put all that many miles on this car) I pay the same $500 for
labor and somewhere in the $300-$450 range for a rebuilt rack and know
that that part of the car is solid for a long while. 

I'd appreciate your thoughts on what to do.

A couple of other V-8 questions.  First, about 10 seconds after some
cold starts I hear a medium sized clunk.  I'm curious as to what this
is.  Sounds like something pressurizing and actuating.  Could this be a
differential lock?

Second, on slow hard turns in either direction, like coming out of a
parking space, I can feel a very slight vibration in the steering.  I've
been told that this is a normal Quattro artifact, but would appreciate
either a confirmation of that or a suggestion as to what might be wrong.

Thanks,
Lewis Schnaper