So it was working before?? What do you have hooked into your line-in??
I just want to make sure you know what you're doing. For example, you can't plug a PC Microphone in the line-in and expect to use it. You need the Microphone to be amplified or you need a USB Mic.
Have you checked your system preferences? If the port is broken, then your in trouble. I don't think they can solder a new port on, I think they replace the logic board (motherboard).