repair cost for harmonic gasket behind pulley

Your question is not clear, a harmonic balancer generally bolts to the crankshaft with the crankshaft pulley attached to it, although I think for your car, there is no harmonic balancer at all, just a crank pulley, behind that is the lower engine cover, if that is leaking you'll have to remove it, basically you're almost there to replacing a timing belt. Repair time for a timing blet on your model is about 3 hours, so to replace just the lower engine cover should be less. Shop rates can vary greatly, google what the average is for your city. If you have a leaky lower engine cover, and you've never had the timing belt replaced, you may want to just get that done, that will include a new cover gasket anyhow. No sense going to all that labor and not do a timing belt.

PS: I'm not a mechanic, I don't have access to detailed repair manuals, so it might be possible to replace a lower engine cover without removing the crankshaft pulley. (ie the cover can split around the crank). Ask the mechanic for a more detailed description of what is going on.