It was not. In fact, six hours later, it's still not together. I put that u-joint into the yoke--
So I got the Fiero out of the garage and the Jeep into it. Disconnecting the drive shaft at the axle was easy-peasy; I heated the yoke with a propane torch and then hit it with PB Blaster, and the bolts simply unscrewed. They've been in there since the truck was built in 2000, and driven through fourteen Illinois and Indiana winters, but they came out nice and easy.
Too easy, as it turns out.
Getting the old joint out was difficult. It's been in there a long time, and it took time and propane and PB Blaster to get it loose. I did eventually get it out, and spent some time deburring the bearing cup bosses.
When I went to reassemble with the new U-joint, it went together nicely...but I could not get both of the retaining clips in.
Og suggested--via IRC--that I take it apart, because it was possible that one of the needle bearings had fallen out or gotten cocked; and when I took it apart, I found that one of the needle bearings had shifted, and in fact had gotten crushed. It had shattered inside the bearing cup, and I said many bad words; I took the remaining bearings out, cleaned them and the cup, then reassembled with fresh grease and one bearing taken from the old u-joint. (Og says a bit smaller is okay, and it fit fine.)
But the thing would still not go together correctly. It was fine until I drove the cups in far enough to get the retaining clips in; then it would get gronchy and not move freely. I disassembled and reassembled the thing about four times.
Finally Og suggested measuring the width of the yoke. When I did that, I discovered that the yoke was a smidge wider than 3.25 at the outside of the retaining clips. The u-joint itself, with bearing cups, is 3.218 inches. The clips are about 1/16" thick; there's perhaps 3.125" between the inside surfaces of the clips...meaning that the yoke is "sprung".
"Sprung", in this sense, means that the yoke is no longer the correct width. Either overzealous hammering or too much force in the vice; either way, I bent it so that it's a bare tenth of an inch too small.
Og's suggestion was to put the old bearing cups and clips in, with some arrangement to apply a spreading force on the yoke. It took some doing but I took a nut, a bolt, and a small socket, and bodged it together; now it's sitting out there with some pressure on it, and it should spread back apart during the night. Hopefully in the morning or afternoon I can get it all put back together.
The only thing I did wrong--other than hammering the shit out of it--was neglecting to mark the orientation of the drive shaft with respect to the rear yoke. But if that turns out to be wrong, it shouldn't take a great deal of effort to correct; it can only go in two ways, and I've already done the hard part of getting the bolts free of fifteen years' worth of rust. And it'll be obvious if it's wrong, because it'll vibrate.
The squeaking noise was happening at the right frequency to be related to my shimmy, though I don't know how the vibration could get to the front wheels when it's in the rear drive shaft. More likely it's entirely unrelated.
Either way, I now know how to get the front drive shaft off, and can check it at my leisure. As if I had any.