Revising an old thread that I commented on. I let my engine light stay on for a while and finally took it in for other service to an indy and had him verify the codes. He found that the 2 "front" O2 sensors need replaced. His quote was $750 all in. Seems high, considering the parts are about $130-$150 each?

Based on the realoem diagram
RealOEM.com * BMW E70 X5 3.0si Lambda Probe Fixings

It looks like I need number 1 and number 2. But I'm still trying to find a good DIY with pics for a 2008 E70 3.0. Looking at my engine, it looks like there's a fair amount of stuff to remove first to get to both of them, but some guidance from anyone who's done it before would help.