Smartin,

Yes, the heater core is centered over the transmission but the coolant will drip out from the lowest part of the plastic box that has the heater core in it. If you have coolant leaking out where you say it is, it is definitely from the heater core or one of the connections to it.

If your car is similar to my 300SD, the pipes from the heater core are connected by rubber hoses underneath the air intake grill below where the wiper shafts go thru to the outside. You could have a leak there and that would be easier to fix than removing the heater core.

P E H