Good Good Good Good Vibrations (well, eventually...)
30 minutes - 2 hours
My iPhone vibrate motor got very loud when it was activated, then a couple weeks later, stopped working altogether. After a bit of research, it seemed worth it to replace the motor (any troubleshooting that involved not replacing the motor basically involved all of the repair steps up to replacing the motor, so figured give it a shot).
It went amazingly well! I followed the repair guide almost exactly. It took one hour and 52 minutes. Definitely used the comments as well as the steps. I used an egg carton plus an additional storage vessel with many compartments, labeling each one as I went with the step and color for each screw. Also laid out white sheets of paper under where I was working. And I taped the egg carton to the desk, for when I inevitably bump it and send it flying. Definitely a good choice.
Take your time and seriously label everything. Note when removing odd little grounding clips and covers, as putting them back in is easy, as long as you take your time. I used a second person a couple times to hold a tool against a screw, help pull tape back, label things, and for overall moral support.
iPhone 4S and iPhone 4 (CDMA) Vibrator
Phillips #000 Screwdriver
P2 Pentalobe Screwdriver iPhone
iFixit Opening Tool