I have a 1996 Pontiac Bonneville, ( OK, so I don't hear any flack.. I know it isn't a Chevy Truck, but it has great bucket seats)
Anyway, the A/C was acting up, so I too it to a GM dealer... they told me it was a bad compressor and that it would cost somewhere between $1,000 and $1,200. I went and got a second opinion, from someone else I knew... Turned out to be a blocked orifice tube. The repair cost about $150.
be careful and always get a second opinion. You wouldn't want to get a heart transplant if all you needed was an antacid tablet, now would you?