My boiler job had apx 32 hrs on a simple install, 8 hrs fixing issues.
They knew what they were doing as I know them and saw the job
completely. Im sure with getting everything together 40 hrs was figured
but near 52 was spent total on a small residential unit. Your boiler is
not old, why replace unles a condensing unit is used, a regular unit
will be apx the same in efficiency. Depending on unit you buy and labor
and local rates who can say, nobody.