Used X5 4.4 question

[RC51]

I'm new to the forum and i'm in the market to buy a used 4.4 X5. Can anyone give me some pointers on what to look for. I have owned several vehicles and I know that once you own one you know all the ins and outs. I am for sure getting a sport package. But, what about mileage? At what point should I say that's to much? What about Nav? Should I want or not want it? I've noticed that there are some options on the members that I'm not aware of like cold weather package. How about the years 2000-2003. Are there any major improvements that I should know about. Is it worth spending a little more to get say an 03'? Any help would be appreciated. I will be doing this real soon and don't want to be unhappy with the purchase. Thanks