Zone valves - trianco heatmaker - where are they located?

Hello everyone. I am a novice!
I have a trianco hw m2 series boiler.
Two zones. one of the zones has head constantly coming up, even with the thermostat off. The other zone is fine.

I suspect the zone valve for that area is stuck open. I cannot tell from the manual where the zone valves are located. Are then in the unit, or outside the unit? and how can I physically identify them? Are they easy or hard to unbolt and replace? is this something I can do myself without "breaking" something?

This issue started today. I've made sure both thermostats are off. In one zone, the head stops coming up into the baseboard (our unit uses gas, the hot water flows into the baseboards). The other zone, with the thermostat off, heats up and continues till the room gets into the high 70s low 80s, ie, just keeps coming up.

I've hit the off switch in the boiler closet. Waited an hour. Heat obviously came down in entire house (condo unit, one level). Turned switch back on, unit cycled, came on line, heat in both zones, one zone was fine, stopped heat when temp in that zone hit 70f per the thermostat. Other zone, hit 70, did not turn orr, continued upwards. Even with that thermostat off, heat continued to come up.

I live i Peekskill NY, anyone recommend an independent repair person?

Thoughts, tips, help?

Thanks,
Nelson Davis