I have owned several BMW's and yesterday looked at a 2004 3.0 diesel E53. Have committed to buying it as soon as our house sale goes through (15th June). My current daily driver is a '97 E39 touring with 293,000 kms. The E53 is a 2004 with 159,000 kms. Apparently the swirl flaps have already been addressed, so I am hoping for several years of trouble free motoring.

Anything else in the way of preventative maintenance I should be aware of?