Hi A Neighbor 2! Our current home has a steam boiler. We learned the hard way that most HVAC guys know, in theory, how a boiler works. But most of them have little to no experience working on steam boilers. If you've got a boiler, and not the furnace with forced air, you want someone that works on only boilers. Call The Steam Whisperer. We tried using a regular HVAC guy last winter, and he blew up our boiler, and nearly our home. Ended up needing a brand new boiler to the tune of 12k. Dave and Matt at the Steam Whisperer will get you sorted. They're not the cheapest, but the do the best work. We'd be about 12 grand ahead in life if we had just called them the first time around. Good luck!
One piece of advice. Go with the established, family run businesses. Father & son joints. Places like Elm, Four Seasons, etc. have too much turnover as far as their technicians go. You never get the same one twice. Those companies are always trying to up-sell also. I had Four Seasons out to inspect & clean my furnace one fall. After taking my furnace apart, the tech announced he wasn't comfortable working on it in it's condition. After he left, I cleaned and reassemble it myself. I continued to do this myself for the next "seven" years with no problems!
Most of the people we have had here over the last 30 years didn't really know how to deal with an old steam boiler. Murray Heating 312-401-6306 Bob has been keeping our antique running for the last 15 years.