I finally got around to doing the job yesterday. Here’s what I found out, in case it helps someone.
The part is “window channel,” Dorman 924-249. It’s roughly 15” long, and has a U-shaped channel on one side (for the window glass) and a C-shaped channel on the other (for the regulator rollers). It’s the same part for the driver and passenger sides. The old part is glued to the window glass with a pretty tough adhesive/sealant.
I used a utility knife to remove as much of the adhesive as I could, including slipping the blade down along the glass into the channel on both sides. I took it slowly, because of course the window is tempered glass -- so one mistake, and it’s “game over.”
I then gently tapped on the channel with a piece of wood, hoping to free it. Then I tried the same with a very wide putty knife. No luck. I finally ended up using an angle grinder along the bottom corner of the channel. I made several light passes, making sure the piece remained cool enough to touch. (I didn’t want to create any hot spots -- that “tempered glass” thing again.)
After five minutes or so, the bottom edge of the channel had been weakened enough that I could peel the side of the channel back with my fingertips and remove the part.
At this point I could see that the window rested in a thin black plastic channel, which in turn rested in the part being replaced.
I left the plastic channel on the window. The new metal channel was a little too tight, so I expanded it until it fit. (I did find that warping the U-channel also warps the C-channel on the other side of the part. It may take some patience and a few tries to get both sides just right.)
I inserted the window/old plastic channel assembly into the new U-channel, using Permatex Ultra Grey as my adhesive/sealant. I let it dry overnight and reinstalled the window. So far, so good.