Wiring this system with my existing furnace single zone system

It's a different independent system from the hydronic boiler and radiator system you currently have. In addition to adding and changing some wiring there's also going to be some pipe work that will need changed and added. You will be basically adding a zone to the current system. You should have everything checked out by a professional to ensure that your boiler, auto fill valve, and whatever else is involved can handle the extra load of the radiant heat zone. It's awesome heat and well worth the effort. Good luck with everything.