So I ran into this problem too. What I did is go to the Bosch website and look up the P/Ns for a 2006 525i (which has the same N52 as in the '06 325i E90). This is what I found:
01 REGULATING LAMBDA PROBE L= 1400MM 1 11/2005 11787558055 $215.65 177.62 Bosch 17098
02 REGULATING LAMBDA PROBE L= 910MM 1 11/2005 11787558073 $215.65 177.62 Bosch 17099
So I think you have the correct P/Ns. Regarding your second question, you are correct, BMW recommends replacing the sensors at 120K. I had one of mine go at about 100K a few years ago and Tischer was selling it for only $55 back then (wish I had bought all four sensors back then). BMW has now jacked the price to $177 because it is time now where the '06s are all getting over 100,000 miles on them. I have 190,000 on my car and have not yet replaced the other 3 sensors. I am going to wait until the error codes come up for them. I keep explicit MPG records on my car, and have found the total MPG has dropped from an average of 27.6 MPG to 27.1 MPG in the last 100,000 miles or so. I chalk the mileage drop up to old age (maybe it's the O2 sensors, but maybe not).
As a side note; on my '99 F150, which was running like crap, a few years ago I replaced all of the O2 sensors at the same time, and noticed no increase in MPG. I replaced them along with the plug wires, plugs, and coil pack. It ran much better, but really did not jump up in MPGs.