I already have PC cards that work with Airport and 10.3.9. I'm looking mainly into eliminating clutter or having to switch out PC cards for different purposes. That way I could just have my card reader PC card live in the slot.
Another question, of course, is will the Pismo still be working after I replace the sound/power card, hoping that then I will be able to power it up with a cord instead of just with batteries.
It's kind of daunting knowing that it will require taking it so completely apart, making so many chances for something to go wrong. I am actually considering looking into having my local Mac house do the installation. (I probably won't, though.) 
Another question, of course, is will the Pismo still be working after I replace the sound/power card, hoping that then I will be able to power it up with a cord instead of just with batteries.
It's kind of daunting knowing that it will require taking it so completely apart, making so many chances for something to go wrong. I am actually considering looking into having my local Mac house do the installation. (I probably won't, though.)