I recommend Tony 4305-5152. He's matriculado. His son installed my gas heater & father Tony replaced the faucets in my kitchen sink.
He has a walk-in off the street storefront on calle San Jose 1584 in Constitucion. It's a family business sometimes the wife answers the phone.
They don't speak English. Very responsible & reasonable. Highly recommended.
Thanks for the recommendation. And thanks to those who sent me recommendations via pm. I'm still looking for a gasista. I'm in coghlan so the gasista should be based more or less nearby or be willing to travel.