Guitarport Through Amp and Recording

No idea if this is going to work or not, but my plan is this:

Guitar is input to the Guitarport, connected to the laptop. The sound of the Guitarport track and the input guitar is normally output to computer speakers. The Marshall head I have has a CD input, however, so I'm going to try to put it through there. I'm guessing that the CD input on the head bypasses the guitar effect channels (clean and overdrive), and I'll get accurate Guitarport sound out of the cabinet at higher volume (almost like having Black Sabbath do a gig in the basement, heh...heh).

Now, when recording using Audacity and Guitarport, if you select Guitarport as the input, you only hear the guitar you are playing, if you're playing along with a track. The end result I'm going for is to have it record it all, so when I get comfortable with a song, I can select the Guitarport track with the guitar removed, so when I record, it's just my playing being recorded with the track.

So, I need to somehow get Audacity to capture both Guitarport guitar input and Guitarport track. If anyone has tried doing any of this before, your insight would be appreciated. Otherwise, I'll let you guys know how it goes.