If "shot" means that it is making loud sickening noises, or even a loud rattle or hum when engaged, you MUST replace the rec/drier and the expansion valve, as well as flush (with a professional a/c flush tool made for this purpose) the entire stystem including evap (with exp valve removed) all lines with NO exception, and both condensers. This would be the time to convert, but if you have a noisey compressor and do not do a major complete flush, you will be doing the whole job over in a few months when the residue of the bad compressor travels throughout the new clean system and makes it a new old dirty system. This is the cheif reason that more NSX owners who contact me for advise- 6 or more a week this time of year- do so; their dealer is telling them that they need a whole new system. EVERYTHING! Hoses, condensers, compressor, evap, drier, etc. Castrol, as well as other companies make a great product called A/C system Flush, for conaminated system. The tool is not expensive, but requires a fairly high powered, long winded (storage capacity) compressor to operate. If you want to do some DIY on the job, remove the blower to access the expansion valve (don't let your dealer BS you that expansion valve requires dash and evap removal, I get that call several times a season). Discard the expansion valve. Remove the rec/drier- discard. open the fittings between the pair of condensors and both lines (do NOT discard.) And lastly, remove the fittings from the compressor. If the compressor is bad/was very noisey, discard it. Find an a/c shop who will flush everything for you with professional grade equiptment and people, take with you some small baggies and tie wraps to seal the clean system for the ride home.
After you install all your parts, take it back to the guy who cleaned it for you, and have him charge it. The kits they sell for DIY a/c system charging is really a bad idea. You need a really good set of gauges to do it right, plus a vacuum pump to remove all the air, moisture, and possibally residue of cleaner. (A/C cleaner is one of those zero residue,MOL, like brake clean, so there should not be much. But there are alot of low point traps in the lines where liquid flush can stand- make sure it is ALL blown out. It will displace freon and diminish your cooling capacity.
With an ambient temp of 100 degrees and a humidity of say, 40%,
the temp coming out the vent should be about 43 degrees if all is well. And that is not on high speed fan- temps go down set to high because of lowered "dwell" time. Test at 2/3 fan speed on recirc only, best with car moving to augment condenser fans with fresh air movement.