Thanks for the responses! I had already gotten this taken care of by the time replies came in, but for anyone else who might come across this post, here's what I've learned:
In my area, anyway, if the testing is done by a certified meth decontamination specialist, they will be legally required to turn the results into the county within 5 days if it comes back over the legal limit. The county comes to red-tag/condemn the property and tenants may only have about 15 minutes to move out if you don't tell them ahead of time. Any belongings in the house will be considered 'hazardous waste' and will cost extra to dispose of. And at that point, it becomes illegal for anyone to enter the property besides whoever is listed on a county-approved work plan. If the permit gets pulled and the work plan is submitted before the county comes to tag your door, it is possible to have the tag placed on the inside so that the neighbors won't know about it. And then once the decontamination work is complete and it passes the retest, they take your property off the list, and you aren't required to disclose it was a meth house to tenants or buyers.
If you just use one of those DIY mail-in test kits, the county doesn't find out, so you will have more flexibility in how you handle the situation.
The prices the meth remediation companies quote you are legit to get the meth residue levels on exposed surfaces in the main living area below the legal limit and get the house un-condemned, but if you do a bunch of remodeling afterwards that involves cutting down walls, cutting holes in the ceiling, sanding through previous layers of paint, etc., you might be re-releasing residue in the process.
Also, it is a very wet process that is likely to cause bubbling on paint, vinyl flooring, cabinets, etc., and any porous material will need to get thrown out (carpet, curtains, etc.).