Dock connector contacts had broken off (kid jammed phone into his pocket too many times).
repair was easy peasy- just like the tutorial. I hit a snag w/ the tiny screws on the outside of the phone when I stripped one and had to use ifixit's how to get out a stripped screw tutorial. After that it was smooth sailing.
Print out the iFixIt page w/ the picture of the inside of the phone, then put down some double sided tape over the photo so that all the different screws won't get mixed up if your kid runs through the room and bounces a ball on the table.