Home button did not work, and the noise-cancelling mic was cancelling all sound, so no one could hear me talking on the phone.
Home button swap was successful. The power cable guide was missing a step to remove the headphone jack, so I accidentally broke that cable when removing other pieces. It's my fault for not being more careful, but I was very surprised the guide was missing that step (I added it in, not sure if it made it into the official guide or not).
Outcome: Home button works, as does the noise canceling mic. The proximity sensor no longer works, and apparently there is some kind of filter that needed to be moved from the old cable to the new (also not in the guide). Since I cut the headphone cable, the volume controls and vibrate switch don't work. Time for another iFixit order!
Total time: a little less than 4 hours to do both.
Make sure you are not skipping any steps! Whether it is due to your negligence or the guide's, skipping steps can be disasterous. Be careful while you are in the phone, it's delicate.