A little more info...
Upon closer inspection I found another access port, this one on a line between the fan box and the evaporator (I keep my ATF and oil funnels wrapped in a plastic bag under the hood, which was covering this line). This one appears to have no pressure at all, and the line between it and the evaporator has a small kinked section. The crushed portion looks to have been kinked intentionally by a previous mechanic. Could this indicate a problem elsewhere? I'd imagine that this line would need to be replaced (at least) before recharging.
I did find one good thing at least. Before I noticed that problem I disconnected the sensor on the condenser and jumped the leads on the connector. The compressor clutch would engage with the appropriate settings on the HVAC controls (I only tried a couple of times, for a couple of seconds each time). Hopefully this means the elecrical portion is up to spec at least. The compressor didn't sound too bad at all, and the revs came up slightly when the clutch engaged (but not as much as my brother's gutless Pathfinder... lol)
Too bad the body is starting to show some really ugly rust. I don't know if I should keep it or patch it up and sell it before it's totally worthless.