Valve covers do not seem to be leaking.
Belly pan covered with oil 100 miles after oil change.
Oil is concentrated on left side beneath the drain plug.
Tried tightening plug, but did not want to force it.
Above the drain plug there is a hose to tube coupling coming from radiator (tranny fluid?) that was soaked with oil also. Tried tightening but seemed very snug.
Let engine run for 15 minutes to see leak, but could not see any.

Maybe I should take car to a pro.