I would push for your ext warranty company to pick up the tab. Who knows, maybe there is a Santa. lol
IF not... you can buy a water pump and thermostat kit for about $510. Like from
Tischer BMW or
United BMW or
Turner Motorsports.
Here is Tischer's...
http://www.trademotion.com/parts/200...iagram=1980080
Most dealers are charging about ~$1,300 I think. parts and labor.
This link might be of interest to you...
how long did your first water pump last?
http://www.1addicts.com/forums/showthread.php?t=765338