A normal tank water heater is like 60% efficient with 75% thermal efficiency, a tankless may be 90%, saving about 1/3.
Is it worth paying like 3 times as much for a tankless considering amount of energy used to heat water?
I don't think so!
I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.