of the mold. The fungus itself extends into the drywall, so abatement via surface treatment will be difficult and require many successive applications while keeping the area extremely dry and inhospitable to mold growth. In other words, it will come back as long as the drywall aint dry.
The good news is that the spores are the part that will affect your breathing, so if there isn't anything left on the surface to produce them, you will likely be OK as long as you don't drill into that part of the drywall.
A weak bleach solution in a spritz bottle combined with scrubbing will kill surface mold. Unfortunately, it also leaves some moisture behind, so you might want to direct a fan onto the surface after you spray.
Another strategy is repainting the area with a paint containing a fungicide, available at most paint stores, but again, this will work only when the drywall is completely dry again.
I'd keep the pantry empty until you're sure that drywall is again dry and have painted with fungicidal paint. An empty pantry will be easier to treat than a full one.
You're correct to say that the drywall should be removed, along with any insulation that has become wet. Unfortunately, this is unlikely in any housing approved for Section 8. Reducing the problem is the best you can possibly hope for. Part of that will be to keep that pantry closed and wearing a mask when you have to enter it for any long period of time.
More info at
http://www.inspect-ny.com/sickhouse/CleanUpMold.htm