I did mine using musicmatch
http://www.musicmatch.com/ , which I have had for years. I used the line in jack socket, and with trial and error you can get it pretty good. It also has a feature which will stop recording during silent bits, but restart when the sound starts again, so it's useful for LPs, but again, trial and error comes into this if you have any tunes with breaks or quiet bits.
To be honest, whatever method you choose, I think you will have your work cut out. Remember, it will all have to be done in real time, and if you have a lot it can drive you nuts.
In the end I basically recorded the tracks I wanted IF I couldn't get them from say filesharing - if no-one else had them I had no choice.