How much should I pay to replace the AC compressor on a 2010 Honda Odyssey?

The air conditioning on my wife's minivan recently went out. I had her take it to a mechanic expecting a refill situations costing less than $100. When they got back to us they said the clutch would not engage on the AC and it required replacement costing over 1100 dollars. I've seen the part online for $250 to 450.

How much is reasonable to pay for this repair? Would I be better off buying the part online and having someone else install it? I'm told the job is about 3 hours.

You are better off paying some guy from the dealership (if they have a mechanic!)

Where is the compressor, does the sub-frame need to be lowered to removed it?
What about bench time to disassemble said compressor and r&r clutch and coil assembly?
Or are they replacing the whole compressor and clutch assembly together?
Is a new receiver/drier (or accumulator) figured into the estimate?
Is it a dual front/rear system requiring almost double the refrigerant?
Is the diagnostic time added into the estimate or are they giving that away for free?
What is the breakdown of parts and labor?

Help us out a bit here with a few more details…