sbright33:
Just make sure the voltage is between 0-5v to go into A/D. You need to choose a time interval to measure the sound level. During that time look for the maximum and minimum sample value. Subtract. Scale to a range you want. I can write you some pseudocode if you like. You can fill in the details.
Thanks a lot for offering your help, but I actually have no idea about the hardware part, I'm finding very interesting things from google results but nothing telling me what components I need and how to convert a line audio signal to a 0-5V signal.