Update on this:
I practically gutted the thing and pulled all the non-integrated components off the motherboard, but didn't find anything physically wrong with them, with the exception of the terrible thermal interface, which I re-engineered (it now runs MUCH cooler - more on that, here:
Gateway Laptops: a Thermal Nightmare [and Fix]. ). The PCMCIA slots still do not work, however I discovered an internal mini-PCI slot hidden below the motherboard, and immediately ordered a Broadcom BCM94306MP mPCI wireless network adapter from ebay for like $12 after shipping. It arrived and worked like a charm after finding the appropriate drivers on driverguide. Now I'm reinstalling Windows, again, because the Belkin/Ativa drivers I already uninstalled did not really go away and were causing random BSoD phenomena on startup. It's going swimmingly... just taking up a lot of my time.
I also got a free battery from Gateway to replace the old one, because it turns out my battery's serial number was on the recall list for explosion hazard.
In the end, I'm retiring this laptop anyway, but still want to use it as a second monitor for my desktop and extra clock cycles for Folding@Home. Its role as my mobile notebook PC has been displaced by a new MacBook... which has troubles of its own.