I think the boiler is the right size, that is, small. One thing I would do no matter what happened is to have someone. It may be a better option for you to review the costs of installing a new natural gas boiler as a better option for your home. This cost estimate generally includes removing and discarding the old unit and all the lines and wiring necessary for the new system to work properly.
Consider replacing a water heater that is more than 10 years old or if repair costs exceed 50% of the replacement cost. You'll need to consider major cost factors, such as the brand, BTU needs, the type of boiler, and what you can reuse from your current heating system. There are numerous types of boilers and many things that can go wrong with them, leading to a wide range of costs associated with repairing them.