Basically the answer to your questions are NO dont worry about the maintenance at such a young age, no matter whether its being sold to you new or used the service interval is still 15k miles, I mean thats a no brainer. Just look it over real good and listen for any possible problems. Its a 325 AWD so the chances it was abused heavily are less of a factor, but you never know with those AWD systems.
Secondly on my 330i Yes its 15K miles and Yes it uses Castrol Synthetic oil.
Thats a really good price. Take it.
<img src='http://members.cox.net/inelson5/330i.jpg' border='0' alt='user posted image' />
<img src='http://members.cox.net/inelson5/wooani.gif' border='0' alt='user posted image' /> The whistles go WOOOO!!! *BUBB RUBB FAN CLUB*