The thermostat is connected to the water pump with two bolts. There are three further bolts connecting the water pump to the crankcase. In theory you could leave the thermostat connected to the car after you remove those bolts and the thermostat -> water pump hose but you'd have less room to squeeze the pump out, maybe not enough. It's easiest to remove both parts at once I would think.
The sway bar needs to be lowered to access the pump as well. Four bolts, takes seconds.
I haven't changed one on an XI but it should be the same procedure and parts. Pumps are the same across the line with the exception of the M3 and 335d, which both use belt-driven pumps rather than electric.
Last edited by PINeely; 03-06-2013 at 05:35 PM.