The easiest way to convert your LPs over "legally" is to get something that can record audio in a fairly decent format. I personally used nero express essentials (came with my burner).
The next thing you will need is an "attenuater", which will clean up the audio signals.
After that, go to radio shack, get a pair of RCA->headphone cables and some rca-rca stereo cables (they have the attenuater as well). Connect it all up to your Line-In jacks on your sound board, and have at it.
Note, if you don't have Nero, Audacity will do the same job, and it's free, if memory serves.
I had to do the same thing with a few cassettes a while back. It wasn't exactly easy, but I got the job done.