High side is low and the low side is high. I am guessing that if you pulled the orifice tube, you'd find the screens loaded with debris. That means the compressor is disintegrating internally. If that is the case, you will need a new compressor (I'd stick with a new A/C Delco). You will also have to flush all the lines and replace the accumulator and the condenser as they cannot be flushed. If you don't and any debris is left in there, the new compressor will not last long. No idea on price, but it ain't cheap. I think the compressor is accessible through the wheel well after removing an access panel.