First the embarrassing part of the story... I didn't pay attention to the W at the end of the part number ... and not seeing a black or white option when I ordered, got the white version rather than the black (yes, the picture was white, but just didn't think about it. I installed it anyway ... may replace it with a black one after I'm done reminding myself of a $50 mistake.
The new touchpad is working fine. I did not remove the stainless steel trim, which covers the edges of the membrane and may help to hold them down. The original membrane pulled out from underneath it. The trim is securely glued down, and removing it surely would have destroyed its smooth finish (with creases, dents, etc). After sticking the membrane in place, I was able to trim about 1/16 of an inch with an exacto knife. Looks good ... except I should have ordered black.