Sorry for the hijack...
Is getting coolant all over the pullies and lower engine block bad when you change out the thermostat? Or does it just make them squeel a bit, and then burn off?
As for your case - I think it is one unit because I've heard if you break off connections on the top side, you need a new rad, not just the tank - but I could be totally wrong.
<img src='http://www.jbheiss.com/pics/BMW.jpg' border='0' alt='user posted image' />