Ancient boiler - replace?

We have a brownstone in Park Slope with a boiler that hails from (best guess) the 1950s. Its a Weil McLain No. 57 Series and has never given us any issues. My HVAC service guy keeps telling me to replace it (because “it’s going to fail on you at the worst possible time”) but is also clearly avid to sell me a new one, so it’s hard to know whether to take his advice. He says it’s so old he can’t inspect it. It has zero controls/bells/whistles that I can see.

I started browsing discussions about replacing old boilers and got the sense there’s a lot to learn. So I reached out to a mechanical consultant /plumber who analyzes heating systems and who, for $1,750, will write up a report evaluating the boiler, analyzing the house’s needs, and giving me replacement options.

So my questions are:
(1) Should I replace the ancient boiler, or not fix what ain’t broke?
(2) Is it reasonable/necessary to hire a consultant for this? If so, is $1,750 what this ought to cost?

pictures of the old girl are attached, for what it’s worth.

Thank you!