[vreihen16]

The glass is only held on by a few posts in springy retainer sockets, and was meant to be removed in a few seconds using a suction cup or two. Unlike an iPhone, there are no gaskets to scrape or anything.

I had an iMac of around that vintage in my office for about 4 years, and swapped the hard disk for an SSD. I'm blanking right now on the details once the glass was off, but I do remember having to use a third-party app to manage the cooling fans because Apple's cooling logic used a temperature sensor in the factory HDD that the SSD did not have.

Anyway, if YouTube doesn't have a video of the process, find a suction cup or two around your house, pop the glass, and see if you're comfortable digging deeper. If there's a free socket and you haven't done it yet, I'd recommend also doing a RAM upgrade while you're in there.....