Larry speaks the truth!
Typically the head gasket leaks form at the rear of the head, but that might be the M104-series.
For the M103 motor, I believe the first sign of doom is oil in the coolant tank. But the front of the head leak is indicative of the timing cover seal, as Larry suggested.
I would contend that the head gasket problem manifests itself slowly, so just keep an eye on it.
If it makes you feel better, I have been watching my rear head leak for three years now...it's only a matter of time, and I just keep putting pennies in the jar to pay for the inevitable.