Is it necessary to drain the oil for an oil cooler seal change? I'm a cheap bastard... well, actually I'm a Porsche Poor bastard... don't want to waste the oil and filter I just put in to get 'er going, but now I have a leak.

more common leak is the pressure sender. Not saying they dont leak, but I'd check the sender first. It sits next to the cooler so it can appear as the cooler is the culprit when it isn't. To answer your question though, no need to drain.

Nope, you don't need to drain the oil.