This was actually an upgrade for me. Work ordered me a new laptop and it came with a low-res screen. I wanted to upgrade to the high-res version.
It went ok. My original glass did get damaged in the process. I think I gave it too much heat, mainly because my glass was EXTREMELY difficult to get off. It took almost an hour of heat cycles before I was finally able to get it off. From all the reviews I've seen, that's pretty uncommon.
I'm up and running on my new high-res screen now though, so it all worked out in the end.
I'd strongly recommending watching this video to get a good idea of how to get the glass off.. They do it a bit differently than the ifixit guide, but it gives you an idea of how much heat you should have to apply, best way to get the glass off, etc: