Xoutpost.com - 2006 X5 3.0I

New member/poster considering purchase of 06 X5 w/53k miles. Navigation, bluetooth, BMW assist. Premium package with xenon headlamps, premium leather, cold weather pkg, etc. Purchasing from private party - what questions should I ask of owner (he is 2nd owner, bought off lease last year)? What other considerations should I make with respect to maintenance, ownership? Owned an 86 318i when I turned 16, and haven't owned a bimmer since. Will be giving up my 01 Toyota Highlander that I did nothing on but oil changes and tune-ups every 30k miles - it has 126k and this X5 caught my eye. Any input/advice is much appreciated!