If you're just playing the guitar alone, with no backup instruments, you can use the output from your mixer to record the guitar simultaneously.
I take just the video output of the camcorder and plug it into the computer.
For the sound part, I take the stereo output of my mixer and plug it into the audio input.
With Premiere, you have to go to the audio controls and select 'rca input' and you're all set. You can play the guitar in stereo straight into the computer and use a decent mic for the instructions.