PCI Compliance class/Certification?

I've been getting more restaurants/catering halls that I manage/install there networks for that run pos systems specifically micros pos. To keep there POS machines and server separate I normally create a separate LAN and firewall rules in between to drop packets. One of my recent installs There POS was connected to a ISP supplied router/modem and I double NATed to keep POS on the ISP router and STAFF/GUEST WifI network on mine to keep it separated. Since I've been getting more customers with this kind of setups that fall under PCI rules/scans I was curious if there are any certifications/classes that I could take so I can offer my customers the best security.

Thanks!