Oh NO! An oil leak and some smoke.

ok, A bit of history. At 101K I had a used motor with 48K put into my 2001 330i. I now have 134K on the clock. This last weekend I put it on Jacks to replace the brakes and front end completely (control arms, links and tie rods). While I was under there with the skid plates off I noticed that I have an oil leak that is minor but has been visibily leaking. My camera battery died taking pictures of the brakes for a DIY write up so I was unable to get a photo of it.. yet. Changed the oil (as always around 5k but switched brands from Castol Syntec to Mobil1) and got it all put back together. I also have been throwing catalyst codes (p0420 and p0430) and it was recommended that I check for leaks and possibly replace the MAF. I found that my intake boot did have cracks in it so I repalced it and the MAF. The codes returned unfortunately. I figure this might be bacause I am running a can of BG 44k through a tank of premium BUT now I noticed the slight smell of oil and some smoke coming from the exhaust... The motor has a two year unlimited mileage warranty on it so I am taking it to the shop to have it looked at in the AM. The shop thinks it could possibly be a bad crankcase valve... (crossing fingers). I just want to know if any of this sounds familiar to any of you? Doing the math the motor is only around 80k and just about everything under the hood was replaced during the swap (belts, hoses, plugs etc)