After changing my oil last night, I took the car for a test drive. When I returned after a 20 minute run, I saw oil streaming out of the back of the engine. I think it may be the rear crank seal, but I'm not sure.
The only thing I did differently was I replaced the 2 tiny O rings on the oil filter cover shaft. They were very hard and had to be broken off. The oil pressure at idle was a little higher than it had been before I changed these- just over the 2 as opposed to just under 2 before. (No, It is not coming from the drain plug...)

The car ran for about 10 minutes at a lower oil pressure at hiway speed... was around 2 on the gauge when I noticed the drop and I immediately stopped the car and put 3 quarts in. Don't know how low it was as I only had 3 qts with me. Drove it home with full oil pressure ok.

Did I damage the engine?

What did I break and how can I fix it? On a scale of 1 to 10 what is the level of difficulty.

Any help greatly appreciated... this is my daily driver and I depend on it for transoportation.

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Mr Goodfahrt (pronounced FAIRT... means "good trip" in German)

1982 300D Turbo Pastel Gray (off-white) 200k+(?)
newbie but willing