Probably not if you are substituting the baseboard for floor heating and it currently can keep the space comfortable. Knowing the BTU output of the boiler and total heat load of the home will be needed to determine if the boiler can handle the load. How old is the boiler?
Are you installing a plastic grid and snap in the PEX tubing then cover over it with tile? To run another zone there are two ways, two circulators or one circulator with solenoid control valves. If you need to temper the heated water, it gets more complicated. If you want to do it as a DIYer, the floor part is easy enough, the furnace part you should get a company to make the modifications.
If you search this forum for user DANA, he has hundreds of post on how to calculate heat loads and many good points on old and new boilers.