I'm the local iPhone tech around these parts!
20 - 40 minutos
My phone stopped vibrating when a call or text came in while in silent mode. Looking around there were those who said "just give it a whack in the palm of your hand... it's stuck..." and I tried it. Worked for about a minute so I found iFixit and found the real solution.
Replacing the iPhone 4 vibrator mechanism is definitely not rocket science and I'd say just about anyone can do it. Get the appropriate screwdriver for your device and you're off and running. 2 screws is all it took and a pair of plastic tweezers (not required but helpful) to remove/handle it. It's so easy, your grandma could do it! Er uhh... well, she could watch while you do it. Easy as 1,2,3.
This was easier than replacing the battery in my phone (and that was pretty darn easy). With these two repairs, my phone is is as good as brand new. If anything else were to come up, I'm certain that iFixit would have the part AND procedure for me to fix it!