4 Wheel Drive/SUVs: Cost: A/C repair 2000 Chevy Blazer, genuine gm parts, chevy blazer

Question
Thank you for your advice.  
The buyer is also selling with vehicle a "warranty for 100k miles"  which he purchased when he bought the vehicle (at 40K) several  years ago.  He has told me it covers the drive train (4wheel drive and all).  
Is there a special name for the warranty that you are recommending?

Paul

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Followup To
Question -
I want to buy a 2000 Chevy Blazer and the A/C does not work.  
Blazer is a ZR2 and has about 66K miles.  Car mechanically runs fine.  I DO NOT WANT TO KNOW HOW TO MECHANICALLY FIX A/C, I want to know how much it costs to fix.
It blows out air but it is not cold.  When I looked under the hood, the belt operating the A/C unit was working but the plate in the front of the unit (which should rotate) was rotating but continually going on and off (with a clicking sound).  
Also, the cold metal hosing (leading from the unit) did not get cold.  
I want to buy the car, but I need to know how much it would cost to repair, so as to deduct this cost from the asking price of the car.  
Do I need a whole new A/C unit or just some refrigerant?  
Also, I want to make sure I am getting genuine GM parts, because I am assuming they are more reliable than a knock-off brand.  I DO NOT want any mechanical info how to repair it.
Any help would be appreciated.

Thanks,
Paul Braun

Answer -
Paul,. the only sure way to know the exact cost is to take the vehicle to your local Chevrolet dealer for a Complete check-up and estimate of total repair costs.  You may have to pay as much as a couple of hundred dollars for this but will be more than worth it in the long run.  While you are there you should check into an extended DRIVE TRAIN warranty which will protect you against major expenditures.  If the seller is unwilling to let you do this I would be very careful about dealing with them.  Best of luck to you.  Bud

Answer
Hi Paul, if the buyer is furnishing the balance of the warranty that is good IF the warranty is a good one.  I would check with your local Better Business Bureau and also call the 800 number for the warranty and get some references.  Make sure you know what the terms and conditions are, including the deductible, and that you can live with them.  Best of luck, Bud