It's not uncommon for an AC repair to easily reach $300. I've done a few already
this season that were close to $1K due to crashed compressors. The compressor alone is
often $2-300 before installation. On a Mitsu Spyder I did recently, the compressor
alone was $450. Aside from a leak at a fitting, AC repair is seldom cheap, and if done
on the cheap it often leads to more costly repairs. On your 17 year old T-Bird, a $500
repair bill for the AC isn't out of the question.
 If you don't fix your AC and the pulley bearing on your compressor is good, the
bypass pulley isn't needed. The compressor will just be along for the ride. They are a
good option if the pulley bearing has failed.

Phhhttt.  $300?  That's pocket change for A/C work.

If you are reasonably mechanically minded you can do your own A/C work
if your willing to invest maybe $300 in tools, and some time in reading the
documentation and understanding it.  R12 systems fall into 2 categories:
those that use old-style compressors that have an oil resivor (York, etc.)
which are worth repairing with R12 (meaning, they will stay fixed) and those
that use newer compressor designs, those are absolutely not worth touching
with R12 because those compressors are generally all sh.t and will blow up
2-3 seasons later.  Any R12 work requires an EPA certification in order to
be able to buy the R12, which costs
time and money (not a lot of it) to get, it's not difficult material to
understand,
though.  There's tons of old 10-20 year old R12 cans on Ebay cheap.  People
hoarded it figuring years later they would make a killing, but
underestimated the
speed at which R134 would come in, they also didn't forsee the government
mandating reclamation which has put a lot of reclaimed R12 on the market.

You can retrofit a R12 system to R134, it's not hard, but it won't cool well
unless you replace the condensor with a much larger and more efficient one.
If you have space in the body of the vehicle it might be worth doing.

Minimum tooling you need is an electronic leak detector, a vacuum pump,
a vacuum guage (which should be part of a manifold guage set) and the
various fittings to connect the freon cans.  If your working on a
charged system you can drive the car to a shop and they can evac the
system cheaply.  That will help you to be ecology friendly.  Years ago
we routinely dumped R12 to atmosphere, I wouldn't do that today.  As
for dumping R134, that's a touchy subject.  Legally you must recover it -
but what the EPA fails to mention is that all medical asthma inhalers use
R134 as the propellant, and there is no restrictions on those, and R134
is used to form bubbles in foam insulation manufacture which dumps
millions of tons of it to atmosphere every year, it's the single largest
source of R134 vents to the atmosphere.  R134 was also selected for
it's environmental friendliness, so you might consider the recovery
laws on R134 somewhat hypocritical.  What I have done is to find
a quick-lube place that does R134 charging, tell them there's a crack
in an AC line that is leaking and I went and bought a replacement line
but just need the system evaced so I can replace it.  Lots of times they
will evac the system for free, thinking I will come back with the fixed
system, of course, once I get the system drawn down I just never come
back and I charge it myself.  Considering they get money from the
refiners for the recovered refrigerant, it's a fair trade.  Do this kind
of thing on a slow day, of course.

AC work is just tedious, it takes a long time to do it right.  That is why
it's
so expensive.  It is really one of those areas where the savings to do it
yourself are so large that it is worth doing yourself.  Unlike, say, oil
changes.
With oil changes I have it down to a science I've done them so many
times, but still, with oil at $1.50 a quart and the filter at $5, and my
vehicles
use 5-6 quarts, for me to do the change saves $6 over going to the corner
change place when they are having a sale - it's hardly worth DIY it anymore.

Ted