The expo pass only is good for getting your face and resume in front of hiring managers and company reps. The only problem is you're in music and it's very hard to land gigs in a loud, crowded room where only your resume (and not your audio) represents you. (Edit - many of the larger companies have lines of people wanting to drop off resumes and you'll only get a few minutes with the company rep... just trying to paint a realistic picture of what you'll be facing). It's possible to land work in the expo room but you're going to have to really be unique, to stand out from the thousands of people there, and try and get a bit more time with the person.
I still think it's worth it to go and get a feel for what GDC is like, even just at the expo level! This is especially true if you're already going to be near it so some of your costs are covered. Then the following year you can go out on an audio pass (or something similar) to where you can actually attend talks, classes and do much more learning. GDC is a great event and I'm going back for my 3rd San Fran and have been to 3 Austin GDC events (back when they had an audio track).
I could usually walk the expo floor within one day, maybe two so since that's the only kind of pass you'd have - I wouldn't stay longer than 1-2 days. I don't recall, off the top of my head, if the expo pass gets you into any parties where major networking and hanging happens.