I used a simple cable from a guitar to the microphone on my old laptop and ran the signal through JACK, it did awesome real-time guitar effects back in the day. Electric guitar cables are mono, you can go to radio shack to get a converter for one end of the cable which will go into your mic input... that is what I did anyway.
Maybe try a UCA202 or something similar to add a separate sink control for a usb input. This would protect the analog in port, from voltage spikes and from yanking during that Angus riff. I have tested this.Then tape an rca connector on the end of your chopped guitar cable and you're good to go.
I remember doing the same with Rakarrack and Rocksmith But it's not what I exactly wanted.
Works great if you are in a pinch though... I was amazed at how well it worked with Jack on Linux because I could never do the same thing in Windows. I liked the fact that it handles real-time effects processing very well but some of the effects were not to my satisfaction... With some tinkering and trickery I was able to get sound fairly close to what I was looking for but never enough to find the sweet spot.
If you want good sound, you need professional equipment of course. But it can be sufficient for having some fun with your instrument