If you received a check before you did the work you can be 99.999% sure it is a scam. A money order is even more suspect. And a payment of more than $10-15 per shop should have you on a dead run the other way. Wire transfer part of the check away? You should be galloping for the nearest police station with every bit of the paperwork to turn over as a scam.
Never heard of Peach-Audit Group, but a quick Google yields [
www.scambook.com]
If you want to be a mystery shopper, start reading the sticky threads at the top of the New Mystery Shopper section of the forum and then sign up with companies from the "Official Mystery Shopping Company" list link found at the bottom of every page of the forum. This will also link you to discussions of these companies.