It depends on the shop and brand. Some brands you must be employed by a shop to take the mfg classes. Others can certify you to work on gear you own without any shop affiliation. You would though have to set up some kind of business with insurance and such to work on other people's stuff for pay. What you want to do now is buy two books, Scuba Regulator Repair and Maintenance for Airspeed Press and Regulator Savvy from Scubatools or other dealer. Study them. Then pick up a cheap reg from ebay that you can get parts for, a few tools, and take it apart and rebuild it. See if a local tech will oversee you or let you watch them. Some may not as they won't be able to keep up the façade that some try to. It's not rocket science.
As for the equipment specialty that can vary from instructor to instructor. I have seen instructors teach one of those courses who are not trained tech's and have never cracked open a reg or looked inside a tank. If that is the kind of course you signed up for and that is who is teaching it, get your money back. On the other hand my Equipment Specialty course early on was taught by a shop owner who did service gear, did do tank inspections, and was a very good course. The course I offer is similar to that. We take regs apart and open tanks, service tank valves, and go over setting IP's, cracking pressures, swapping hoses and HP spools, etc. Stuff that may save your dive day.
But get those two books to begin with and study them.