is my head gasket blown when coolant is leaking from the valve cover?

Hello, if you have coolant leaking externally from the cylinder head, the head gasket could be leaking externally, but may not be leaking internally. The term people throw around "blown head gasket" typically refers to coolant leaking into the combustion chamber of the engine -- where it does not belong -- due to a gasket breached internally. External leaks can happen also. But, the valve covers do just that -- they cover the valves, and there is only engine oil in that area.

More likely this leak was created during manipulation of the valve cover(s) - whichever engine may be under the hood.. Visual inspection by qualified personnel will be required. Good luck !