I would try drilling a hole across and thru the pipe nipple, then stick a stout drift punch in the hole to see if nipple will move, I suspect if you can break it loose it will come out. A 1/2" pipe extractor would be another option. (Ace Hardware)
Failing that, the compressor can be detached from the housing without losing the charge. First remove the belts. There is a bolt in the center of the clutch assembly, remove that bolt. The clutch assembly is on a tapered shaft so some gentle tapping with a wood block should pop it loose so it can be removed and gotten out of the way. Once that is done you can unbolt the bracket at the front of the compressor. Remove the rest of the compressor brackets and the power steering pump. The compressor is mounted on flex hoses and it will now be possible to lift it up enough to clear the housing. You will also need to remove the lower pulleys and the harmonic balancer to get them out of the way to access the rest of the bolts in the housing. You will need a puller to get the unit off of the crankshaft. This would be an excellent time to replace the timing chain if that has not already been done. Be sure to replace the cover gasket and the hub seal.
Dave