Finally got my A/C rebuilt and working.

[Raydar]

...just in time for winter.
This is new territory for me.
Since the Caddy compressor died a slow death, and the system had been repaired and patched "piecemeal" since the 4.9 was swapped in, I decided to start from square one, to eliminate the possibility of contaminating a new compressor.
I disassembled and flushed the entire system, including the condenser, evaporator, and all the lines.
Replaced all the O-rings with the exception of the one under the spare tire well. Examined that one, and there was no evidence of leakage, so I left it alone.
Found a brand new compressor that is supposed to be a replacement for the Cadillac 4.9 compressor. I lucked out in that it had a dummy plug that allowed the installation of a high pressure cutout switch, which is MISSING FROM ALL FIERO FACTORY SWAPS. The stock 4.9 compressor just has a blank casting that does not allow for the installation of any switches, as the Fiero compressor has.  Normally, this wouldn't be a big deal, right up until it is. 
Flushed everything with mineral spirits, and then lacquer thinner; then blew them out with compressed air.
So it's done. Cools nicely. I didn't bother measuring with the thermometer, since it's cool outside, but it's blowing colder than it has in a while. 

If anyone has specific questions, please feel free to ask. Having never done this before, I researched this to a fare-the-well before and during the process.

[Roger]

When can you do mine?

BTW: How did you remove the condenser to clean it?

[Raydar]

When can you do mine?

BTW: How did you remove the condenser to clean it?

You have to remove the filler panel from under the front bumper cover. Eight 7mm screws and ~5 10 mm screws.
There is a rubber splash shield(?) at the top of the radiator. Held in place by 5 plastic buttons. Remove that.
Once you disconnect the fluid lines, there are two screws at the top of the condenser and two at the bottom.
When you remove the upper screws, lower your front compartment cover to the middle notch. The washers on the screws can catch on the front edge of the hood, otherwise.
When I reinstalled mine, I had trouble getting the upper screws to "catch" on anything. I don't know if there were captive nuts in the rubber washers, or what.  Wasn't going to take the front of the car apart to see. But it's not going anywhere.

The biggest problem I had with the entire job was that the d@mn couplings want to cross-thread. It's really easy to do so.

[Roger]

Thank you! I hope to get started on mine this weekend (crossed fingers).

It's not a waste to fix it just before it gets cold. When you run the defrost mode the
compressor runs to remove moisture from the interior to prevent further fogging.
This also keeps the oil circulating through the system that helps O-rings and the
compressor stay lubed.

Neat huh?

I have found reams of information about this system that I will post later once I
get it all sorted out.
If only I could find the info I REALLY need (like I got from you :-)

[Raydar]

The most difficult thing about a stock system will likely be the top bolts on the compressor. Strangely enough, the 4.9 compressor seems to be a lot easier to get to, even with the exhaust system in place.
If you want to remove the evaporator core for flushing, it can be removed through the front compartment without taking the dash out. You have to remove everything from the front of the bulkhead, though. Washer fluid bottle, receiver/dryer, blower motor, etc. all have to come out. You'll have to remove the heater hoses from the heater core to get the front cover off of the airbox. Since I had suspected my heater core of leaking, I replaced it, too. Since i was replacing it, I didn't have to remove the hoses "gracefully". I just took some big channel locks and smashed the hoses and the tubes inside them.
All of this stuff is on Pennocks.
For reference... If you're replacing the compressor and flushing the entire system, a "dry" system will require 8 oz of PAG oil and 21 oz of R-134. I put 4 oz in the receiver/dryer, 2 oz in the condenser, and 2 oz in the compressor. Mine actually only got about 7 oz of oil, since I spilled some when I was trying to "prime" the condenser. (They say to use PAG 46 for a new compressor or PAG 150 for a previously used compressor. My compressor was new, but didn't specify on the instructions. I opted to use PAG 100, just because...)

Have fun. If you've never done this before, plan on the job lasting the better part of two weekends. (But then again, I'm slow. I'd starve if I was trying to do mechanics for a living. )

[Roger]

In theory it sounds smooth!
In practice it's 180⁰ out ² times (x) aspirin.
But you gotta do what you've gotta do.