Well, I think I may have made a costly mistake. Changing pads on the rear, trying to get the pistons back in so the new shoes would fit, and I ran the adjustment screw for the outboard piston so far that the lock nut came off. Realizing I had been going the wrong way, I turned the screw the the other way but it didn't pull the piston back in. So grabbed a pair of Channel locks and easily pulled the piston back in, but fluid ran out around the adjusting screw. Now any pressure from the brake pedal and fluid runs out.

Did I ruin a seal and now need a caliper rebuild, or is there a fix without rebuilding?

Yeah, you can say that again.

That's what I thought I was going to be dealing with initially, but I think the adjuster is still engaged with the piston. That is based on the fact that if I manually push the piston back into the bore, the adjuster will push it back out.

The nut on the outer adjuster is supposed to be held in place by a C-clip; this is to keep the adjuster assembly from being drawn into the caliper. There is a tiny, and almost irreplaceable O-ring just behind the nut. If the adjuster gets too far out of position, then the O-ring gets out of it's bore and can be damaged; thus resulting in the leak. Now the whole caliper needs disassembly to replace that O-ring. A good rebuild kit will come with the O-rings, but not all do. In the 30 years I've been repairing these, most of these outer O-rings have been in bad condition, and only in the past 5 to 10 years have they even been readily available. The factory never offered kits, and for a very long time there were no kits at all.
There are several threads on rebuilding, and I've posted photos in the past with all the parts laid out. It is a tricky process to complete, so getting Eric Shea to rebuild them for you is strongly advised.

Thanks for the reply Dave; sounds like that is what happened.

I've search all over this site at on the bird site and have not been able to find pictures of what I'll discover on the inside of the caliper. If you can post a link to the thread you mentioned I would appreciate it.

Parts and instructions can be found here:
http://www.pmbperformance.com/catalog.html

Just finished rebuilding all of my calipers. If they're not stuck (and it sounds like they are not) it shouldn't be too hard.

this thread has a few good pictures:

http://www.914world.com/bbs2/index.php?showtopic=77361