The SuperDrive in my iMac crapped out, but luckily I still had an older model that I had installed in my old PowerBook, also using iFixit, which I had kept after giving my dead laptop to the recyclers.
Well, my old white iMac was a breeze to get into and mess about in, although the repair was a success, I was amazed at how unfriendly the new iMacs are compared to the old ones in terms of getting inside them.
I didn't sit the SuperDrive in its plastic frame correctly the first time so after I had everything back together the drive couldn't eject discs because a bit of the frame was in the way. I had to dismantle and reassemble the iMac twice. Make sure everything is seated properly before putting it back together!