Are they wanting to replace the entire exhaust system? If so, then
$900.00 might not be out of line, but it is likely that the problem lies
solely with the muffler, the catalytic converter, resonator pipe, etc.

I have never had to replace an entire exhaust system at once except when
upgrading from the header/manifold back to the muffler.

Since it is out of warranty, I would find a good exhaust shop and take
it there. The problem might be a lot less expensive to fix and you are
at least getting a second opinion.

Lanny can probably recommend a good exhaust/muffler shop for you in St.
Louis.

Pat

I had a '97 protege, and I had to replace a couple of different pieces of
the exhaust which cost around $400.  The mechanic I went to got on the phone
to call for parts, and when he was quoted the price said "it can't be." It
has to do with the pieces only fitting the Protege.

The local shops around here will custom build exhaust systems for a lot less
than that!

It's likely that a muffler/resonator replacement by such a shop is really
all that you need.

On the other hand, salt on the roads may cause the whole exhaust system to
need replacement.

If you're looking for a cheap solution, there's a junk yard in Litchfield
(probably about 1/2 the way to St Louis for you) that replaced the
muffler on our Astro minivan a some years back for about $60 iirc.  
Unfortunately, if you want to find it, the best directions I could give
you would be the directions we were given: "go to any gas station in
Litchfield and ask where the junk/auto salvage yard is that does
mufflers".. it worked for us, of course that was about 10 years ago.  
Either way tho, it seems rather rediculous that they'd want to replace
the entire exhaust system when, like others have said, it's probably just
a single component w/ a problem.

For comparison/perspective, I recently had a catalytic converter replaced
under warranty for my Subaru.  The cost for just the cat, was listed at
over $1000.  And of course, with typical dealer proficiency, they half-
assed the job and I had to pay my regular mechanic to fix their screw-up.  
Morale of the story, find a good independant mechanic, he'll probably be
cheaper, and you'll increase your chances that the job will be done
right.. the first time.

-Scott