Hi rsherid,
I did some digging for On Call and I was able to find two things, one of which was a place in Chicago and the other was a series of YouTube videos. I'm unsure if this is where you machine was sent out to or what's going on. As the places appear to have different logos it's unlikely that they're the same place.
I certainly understand the diagnostic portion, but that's a couple of hours (max). When I use to service Apple products, there was a series of diagnostics that I would have to perform on every machine, regardless of the issue. This was to ensure that no new issues cropped up as a result of my service on the machine. But typically a cracked screen is pretty cut and dry, unless they're finding issues with the bezel, inverter or something else.
http://www.classifiedads.com/tech_services-ad1908401.htm
http://www.youtube.com/user/oncall258
I figure it's unlikely that Micro will let you call the vendor (I can't imagine they would) and I've yet to hear of place that allows you to post pay for expedited service on something.