It's a more "involved" fix, but very easy with the instructions from iFixit!
Bought the 4k Retina iMac from Best Buy for a great price, and didn't even thing about the fact that I was getting an HDD. Oh. My. Goodness. Tough to go back to HDD after getting used to flash/SSD storage. I ended up downgrading size from a 1TB HDD to a 525 GB SSD, but the speed is light years better on startup/login/etc.
Honestly I was scared to do this, but not scared enough not to try it. I ordered the repair kit that came with the little "pizza cutter" tool and new adhesive for the screen, and following the steps it all went incredibly well. Like, way easier than I thought. I did mess up a tiny bit putting the screen back on and there is like a 1mm gap on the bottom part of the screen, but it's not noticeable in day to day use. Overall the process took under an hour and was really easy. One note: I did already have the tools needed for getting the screws off.
Follow the steps exactly, get the adhesive strips (non-negotiable,) and the pizza cutter tool will save you hassle and IMO is worth the extra $5. Solid results from iFixit.