My 2006 325XI, with 115k on it, has a over heat issue. While driving I got a Yellow over heat, followed by a red one a few miles latter. Pulled over checked coolent level which was almost filled. HAd it towed to my service guy, who is not a BMW guy by any means, but honest and dependeble. When we started it up the next day to pull it into the shop, a low coolent level come on? The fault code he got was a high water pump rpm. We removed the pump and it seems fine inpeller looks fine, it semms to run fine, he is going to change out the thermostate, my question is with this many miles on it, and the labor invlolved to get the water pump off, should we just be a new on one, i know ther about $500 but, how much longer is it going to last?