NxLucene Search Result Sorting

I have a local site for my country where people post classifieds for 7
days for free and pay fees for longer period.  I am thinking of using
NxLucene to provide searching capabilities.  What I need to do is:

1. Sort the retrieve data accorinding to newest to oldest based on created_date.
2. Remove expired ads from NxLucene Index periodically every day.
Also if someone post an ad, it should reflect immediately in the
search results.

I am not sure where to start in NxLucene to have these implemented.
Any help, examples would be appreciated.

Thank you.
Peter
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