My wife and I both have iPhone 4s's which we bought ourselves for our anniversary almost 2 years ago. 2 months ago her cellphone suddenly had no sound, I mean from the external speakers but the earpiece and headphones were fine. But one time she plugged her charger cable on, the sound came back but unfortunately the sound went out again after 3 hours. Reading the blogs here in iFixit, people adviced readers to to clean the dock connector by blowing, brushing, pressing and with alcohol and etc... If nothing works it must be the dock connector. So I bought the dock connector and fortunately I bought the complete set of tools from iFix it 6months ago which I have not used ever since I got it. The dock connector arrived and I installed it, I was so excited but when I restarted it, no sound still! I went back to iFixit.com and read blogs again and this time I was directed to the speaker enclosure which I bought and this time with the pro magnetic mat to work on. And voila! Speakers worked very well and I am very happy with it!
The repair was easy this time. I was quite familiar with the screws and this time i used the pro magnetic project mat. It really helped me a lot since I could mark the the mat on which step I removed the screws from. Too bad I did not take pictures of it.
My advice is read the blogs and instructions first related to a part you are working on before purchasing or before working on the project. It was so stupid of me having blinkers just because of the blogs and I concentrated on that part (dock connector) when it was too obvious that sound comes from speakers!