I left mine out. LOL

iFixit has listings for replacements. Go to the Parts section

If by rubber baby buggy bumper, you mean left speaker, then yes, I agree. Reinstall the hard drive before the left speaker.

Here are a couple tips from me:

1) Expose the adhesive to extreme temperatures. I did this by transporting my iMac in my car, screen-down on a piece of cardboard on a cold February morning (in Chicago). When I went to pick up the iMac, the screen practically fell off the chassis. I would have been distraught by this if I hadn’t already planned this replacement. So it was a happy accident.

2) Remember to expell the residual power from the power supply by pushing the power button while the iMac is unplugged. This does NOT guarantee it’s safe to touch, but when I accidentally brushed the solder and exposed capacitors, I didn’t get shocked.