Ok, remarkably enough, the Right Answer to this question should have been "Have you googled?" It never occurred to me that this problem would be so common that Big Business would have been built around it.
Some research:
http://www.buildernewsmag.com/viewnews.pl?id=312
It seems that meth decontamination can run anywhere from a few thousand dollars to more money than my car is worth, and nobody's willing to help hapless homeowners with the costs. The nasty chemicals in question aren't usually the methamphetamines themselves, either -- those are virtually harmless in the kinds of residual doses that are present in most poorly cleaned labs.
It's HI, Hydriotic Acid, and Red Phosphorous, that cause problems. These substances permeate all porous materials. Even if painted over with a sealant-type paint (like Killz), latent humidity causes their eventual release by leeching through whatever paint was used. Heat compounds the release, along with humidity.
The next item of note is that it's extremely hazardous stuff. 2ppm of HI is considered deadly. Smaller doses of HI or RP cause all kinds of unpleasant side effects. Apparently, it's not uncommon to find meth guys dead and rotting next to their gear (and a voice from heaven proclaims loudly, "Justice is Served!"). Therefore, the sites all recommend against doing it yourself. That may be because the sites I found were virtually all operated by professionals who have paid a lot of money for the necessary decontamination certifications, but it may be because it really is that dangerous.
Thanks again for the pointers, guys.