Sadly I can't answer too many of your questions since my situation is slightly different then yours. :-)
I am lucky enough to have an acquantance who works with wireless networks and had some extra equipment that he could lend me so I didn't 'buy' anything. At least not yet. :-) The external attenna is an omni but other then that I am not sure of brand name. I have been doing all of my scanning while driving thru streets at night. Sometimes swinging through parking lots of larger more technical buildings to see if I could pick up anything.
Hopefully someone else will be able to give you actual specs on what they are using. I am thinking about using the specs from
http://www.oreillynet.com/lpt/wlg/448 to make a small directional attenna to play with thouhg. :-)
What I really need is something that will extend that darn Lucent pig tail without dropping too much db. Not sure what the point of having a decent attenna is when it can only go a foot away from card. :-)
John K.