A couple NICO members have recently had trouble with what they thought was a properly working used MAF, one of which went through way too much hassle before he isolated the supposedly good MAF as the culprit. The good used ones are getting older and older. For $400 you can buy a brand new MAF and harness-side connector parts and be sure that the MAF will never be a problem again.
Having said that, many NICO members are running their cars on MAFs they got through
http://www.car-part.com (Air Flow Meter). I'd be hesitant to buy a used MAF from a private ebay seller - if it works, why is he selling it? The one you list claims it's a new part, so that's different. At least take a look at what's available on car-part.