@PCH_BMW,
At 120K miles, sure you can spend 10-12h replacing the oil pan gasket but...it is the OFH Gasket ($5 at dealer). This was exactly what happened to me at 115K miles: oil pooling at the pan, simulating oil pan gasket leak. A few drops of oil on driveway per night.
I replaced the OFH Gasket (did the PCV at the same time b/c of ease of access to the PCV system).
So far so good bone-dry, zero oil leak.
So, start with the common and easy cause first: OFH Gasket. Here is the DIY I wrote:
http://www.xoutpost.com/bmw-sav-foru...-overhaul.html
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On the issue of oil pan gasket: My 1998 528i M52 oil pan gasket is still factory at 160K. This is not an issue until 200K or so. Very often people misdiagnose the problem. See bimmerfest E39 forum for the threads on it.
Now, for people who want to replace the oil pan gasket, there is a technique w/o dropping subframe: just cut the gasket at 1-2 places, install, patch with RTV and you will be fine. See the thread by Mudbone in E39:
Replaced oil pan gasket - Bimmerfest - BMW Forums