Sorry to bump an old thread but I thought I would share my experience for future readers.
I replaced my water pump and thermostat on my 2009 328i AT with 70k miles as preventative maintenance. I did it at home on jack stands in ~5 hours. It's not a complicated job but the process is made difficult by poor access to the thermostat hose clamps and upper WP bolt.
I removed the front passenger wheel and sway bar completely to give myself more space. I did not have to remove the radiator fan but it might give you more access to the upper WP bolt.
I drained as much coolant as possible from the radiator before I began but there is still quite a bit of coolant trapped in the WP and thermostat hoses.
I removed the U hose first, then the thermostat and the WP last. The thermostat hoses are a huge pain and I actually found it easier to remove the forward facing hoses from the engine bay (after moving the reservoir hose out of the way). Silicone spray helps a lot with the removal of the hoses, including the clip ones.
I reinstalled the thermostat first, then the WP and the U hose last. Installation is much easier since you can orientate the hose clamps for better access. My car took just under two gallons of coolant and I did the bleeding process three times for good measure (with a trickle charger connected to the jumping points).
I bought a Pierburg pump (included the 3 bolts) and a Wahler thermostat (came in a Behr box) and they were exactly the same as the original factory parts. The original and replacement parts have date markings so you can verify their age.
The DIY here, along with the following resources, were helpful:
http://www.pelicanparts.com/techarti...eplacement.htm
https://blog.bavauto.com/14581/bmw-h...55-6-cylinder/
Good luck!