Just to complete this very thoughtful discussion:

A couple of days ago I've been reading around on the net about the mac mini hardware and my understanding is, that to install the Airport card it probably takes an extra (not included) adapter and the antenna seems not to be included in standard models either.

Maybe there will be a nifty hack around this but if you anticipate to need WLAN in the near future without external devices hanging off the USB-port, you might want the option built-in.

Anyway, all the best for your new computing experience !

The Airport and Bluetooth cards are not built-in, but available as inexpensive options at the time of purchase. Both antennas are built-in and ready when/if you add the option in the future.

the airport card definately requires an adapter card. you will probably have to get it from an authorised dealer as an install item, not likely available as a do it yourself thing.

I just read a news item about this yesterday - apparently the necessary adaptor will only be available in a bundle that includes the Airport card and the Bluetooth hardware as well. Price had not yet been determined.
Thus you had better get it built in at time of order if you think you will want it.