Took my van in for and oil change and the head gasket was leaking so they replaced it now the van smells like antifreeze and makes a gurgaling sound like there is air in the system and hums almost like a alternator ..

First double check the coolant level, the gurgling noise is probably from an air lock created when refilled. Check by removing the rad cap, not just reservoir level. Top up coolant level if needed, the noise should go away shortly. The coolant smell is most likely from doing the job itself. If it wasn't drained properly, some coolant will spill onto or even into the exhaust system. When it heats it will smell like coolant until burned off. The hum noise I'm not sure, alternators create more of a whine noise. It could also be from spilling coolant on the serpentine belt, it may squeal for a while afterwards. A good technician will always, drain coolant fully first, and should shampoo the engine after the job to eliminate any mess they created. If any of the noises continue, or the coolant is still low after a few days, return it to the garage for further diagnosis.