Oil leaking on the driver's side back and flowing down onto the tranny is probably the oil filter housing gasket. There are five allen bolts and one is a PITA since there's no clearance to get a regular one in there. Do a search and you'll find advice. ************** claims to sell a special kit with cut-down tools to make it easier. The danger with trying to crank down on the bolts to seal the leak is that now you've just torqued the hard-to-reach bolts you'll need to remove in order to replace the gasket if that repair doesn't stop it. It's a risk vs. reward judgment on your part.

I found getting all the lines back into position a hassle, since you're dealing with the turbo line, both oil cooler lines, the oil pressure line.

The oil cooler hoses are bit pricey, but they break down and start to weep oil over time. That oil flows back onto the engine mount and other components on the driver's side and makes it hard to ID other leaks. The fittings on the cooler seem to be a troublespot in the repair due to corrosion issues between the cooler and the hoses. 27 mm wrench, I think.

The best starting point is probably a can of engine cleaner and high-pressure car wash. Get it as clean as possible, ID the leak, clean it before the repair.