It's your money and your car. We are free in this country to do with our money and property as we see fit, at least to a point, and for now.

$1,200 is WAY too much money for changing the expansion valve. Since you are committed to following the EPA guidelines, I hope that you recovered the refrigerant when you did this job. If you vented it, that would be a violation.

As a reminder, to follow the Federal law, the system must have correct fittings and proper labeling. You must also use shutoffs in your gauge set no more than 12" from the port. This and further information is all in the 609 certification information. There are probably just as many or more violations of Federal law in converting and servcing converted systems than there are in handling R12. Since you are committed to following these laws, which is commendable, perusing the information online would be helpful for you.

Good luck with it.