also check
www.bmwtips.com
there are af few things that do go wrong with the e39 specifically with the M62 motor
1 - the MAF sensors tend to fail
2 - the Radiator (neck) is known to blow
3 - Change the Battery 3-4 years - (they will stop when you least expect iT)
those are the REAL biggies... I have had the MAF go (4-500 - CPO covered these costs)
the M62 (4.4 litre v8) is a real blast to drive... I have the 540iT sport... love every minute of iT
I upgraded to the M5 rear sway bar... really keeps the back end under control during high speed lane changes, turns, etc