Could this be a bad head gasket? 103

[jeffoc]

I have owned a 89 300se for about a year. The car has never overheated or ran the slightest bit hot. I replaced the radiator and fans about 11 months ago, (I hit a deer not due to high temp).
In the past week I noticed I was using a quart of oil in 500 miles. It has always had a slight leak from the front seal. But this was more like a quart every 2k. I checked the coolant and found the mayonaise looking stuff in there drained it and flushed it, but after another 400 miles it is back.
There is no water in the oil, plugs look absolutely perfect, no smoke or steam at the exhaust. But on the back of the engine passenger side oil is leaking down onto the trans.
I have never had a head gasket fail so I am not sure how oil would get in the water but not vice versa. Also what would cause the gasket to fail? Did replacing the cooling components increase the pressure enough to blow the gasket? When I searched this it seems to have happened when the system was weak but my cooling system was fine before.
I drive the car 1k a week and it has 254k on it.
Thanks for any insight into this.