Postscript. I ordered the part from Performance products, and it came in this weekend. As hoped, it was only the black cover, so no painting required.
Removing involved three sheet-metal screws at each end, removing the license backplate and temp sensor, then disengaging all the snaps. Since limited access to the snaps meant removing the old cover unscathed would require a lot of time, and the old cover was to be discarded, I basically ripped it off at this point. Judiciously. Most of the snap tabs were damaged, but the high-impact painted plastic bumper cover I was careful to protect.
I exchanged the foam insert to the new cover, and it snapped right on. Reattaching the six screws at the ends was a little trickier than I expected, but the whole job was completed in under a half-hour. Thanks again to fastbenz!
'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7