My T-stat just went out at 61K miles on my '04. It took an hour at a very leisurely pace to change it out. I followed the DIY instructions for the E46 M54 (found with a simple google search).

__________________
2016 GMC Sierra 2500 HD All-Terrain, Duramax 6.6

2011 X5M Alpine White/Sakhir Orange, Eucalyptus, Spare tire!, Comfort, Soft Close, Tech, Rear Climate, Individual dash, Individual Audio, HUD, DVD, USB, Cold.

Gone:
2008 4.8i
2005 X5 4.8is
2004 X5 4.4i Sport
2004 X3 3.0i 6MT
2002 M5