A/C in my Saturn went out Monday.  

It had a barely audible rattle/hum when set on high for the last few weeks.
The blower (perhaps wrong term) does not even start anymore.
Seems to have been a water leak out of the dash into the passenger floor board.
When it was working the A/C air was not as cold as it was when it was newer but I understood this to be normal given the car is 6 years old.  Perhaps needs some freon.


Any guesses as to what is wrong and how much of a raping I am probably going to take from a mechanic?

Should I avoid a national chain like Firestone, etc.?

You had a problem, and let it go until it got worse.  This usually costs more.

You won't get "raped" as you put it, if you simply make an educated choice about your car repair needs.  

The water leak probably led to the blower motor failure, which means you will need to fix both or the problem will reoccur.  

The refrigerant being low will be an unrelated repair, and it may just need a recharge or it might be leaking somewhere.  Cost of repair varies drastically with the problem(s) they find.  

When the AC in my Dodge Ram stopped working last year, I figured the compressor took a dump and it would be an expensive repair. I took it to a mechanic for diagnosis and an estimate to repair. He said that the compressor clutch had worn out. Said he had seen the exact same thing before on a similar truck. He could have raped me for a new compressor, dryer, orifice, refrigerant and whatever else is involved and I would have never been the wiser. He told me that through his sources he could only get an entire compressor/clutch assembly, but if I could find just the compressor clutch for less he would be happy to install it. I did just that and had him install it. Total cost came to just over $300.

To the Original Poster:

My A/C went out last summer.  One day it worked, the next day it didn't.  The compressor would cut off after about 5 seconds or so and this resulted in the fan blowing air thru the vents but not having any cold air.  One of the hoses had been rubbed gradually by the engine over a few years.  Eventually it just rotted thru and the refrigerant leaked out.  Mixed with the refrigerant is something called PAG oil.  PAG oil keeps your system lubricated and protects the compressor from overheating.  There is a "low pressure cutoff switch" that keeps the compressor from running in the event that the system loses its refrigerant and/or oil due to something opening up the closed, sealed system.

So my blower ran but I had no cold air.  I suspect that your problem is the reverse of mine.  You need to check all of your hoses and piping INCH BY INCH by hand.  Just check out everything you can see, grab, or reach.  Make sure there are no subtle cracks or abrasions in the hoses.  Using a UV dye from AutoZone would help alot.  The kit is ~$20 and has the dye which you inject into the system via the low-pressure side connector.  NOTE:  You must have adequate pressure in your system to find the leak this way.  It MAY or MAY NOT be necessary to add coolant to your AC.

You can very well do all of this work yourself, especially the diagnostic and inspection work.  

Once you know that your AC lines are properly filled and holding pressure you can start inspecting the other components.

Check the obvious stuff first.  Fuses, etc.  I personally fixed my air conditioner last summer and if *I* can do it, ANYONE can do it (I'm a girl)