Success. For any interested people, it's about an hour - going slowly. Now that I've done it, I assume I could do it again in 15 minutes if I had to.

Just have the right tools handy, the T 8 and T 10 bits in particular. Getting off the display screen is easy. The screws are harder than you'd think because of the magnets, but they're not that bad. I recommend having tweezers to help pull them and place them later on.

Overall, the thing that worried me most was the fan issue. And, so far... it's not an issue. I had a seagate 500 gb, and I replaced it with a seagate barracuda 3 tb hhd. Everything fit right into it, just as it did into the original. No optical sensor needed. No new sensor needed, period. No software needed. Nothing. Just put in the new hd, and it works. I'm very pleased, and very proud of myself. Good luck to anyone considering doing this upgrade. You can do it, really.