Do I need an iMac memory module thermal pad?

Well the iMac has been taken apart.

I have found that the previous owner did an ifixit upgrade to 32gb as the modules have the ifixit logo. However they don’t have the thermal pad.

I have 16 gb of new crucial Mac certified ram, which I am about to install but no thermal pad. I wonder is it essential?

if so what size or thickness or type do I need?

I also noticed what looks like corrosion on one of the Bluetooth antennas. Should I be worried? Do I have to replace?

I also found this (a square black sticker) stuck at a random angle on the back of the display. It’s about the right size and shape to cover the cpu, but perhaps it’s supposed to be stuck on the display to protect it from cpu heat?

Any help much appreciated.