Pray.........Everynight before you go to sleep. On a serious note as already said these things are great to drive, but when they go wrong, can put a big dent in your pocket. At the millage you have I dont think you will get a warranty company to cover it without massive excesses. My advise would be to keep some cash aside for those rainy days.
I dont know much about your engine so carn't help you there,but things to keep an eye on are bushes both front and back,C/V joints/boots, and the dreaded transmission.
Dweeb
Remember only the negative sides to owning an X5 are ever posted so dont panic too much.