Can anyone help with heating question?

I am doing a major remodel on my house,(mostly diy). The only heat in my house is hot water base board. I am changing my floor plan and adding a master bedroom and bathroom. I am using gas fireplace to heat the bedroom and would like to put underfloor heating in the bathroom. Can I plumb the underfloor heating into the boiler that is used for the baseboard heat? And since I am only putting it in one room, do I need a manifold? (there isn't one now for the baseboards, it's an old house and it seems to be one giant loop.