For #1 - watch the DTR line in TCP Sockets mode. It will de-assert when the connection is lost, and be asserted when it is connected (you can watch the line on the prototyping board). It really doesn't make sense to inject data on the serial line - how can you distinguish between a valid N and a device sent N?
For #2 - it depends on how you want to allow people to configure the Wi-ME. For example, you can use RCI over Serial (see the RCI Specification and the Command Reference Guides here: http://www.digi.com/support/productdetl.jsp?pid=2469&osvid=144&tp=3&s=54&tp2=0) to configure the Wi-ME over the serial port. If you want to do it over the air, you can do so, but the Wi-ME has to be connected to something first. You'll also want to make sure that the end user can factory default it if you only allow updates wirelessly. By default, the Wi-ME will try to connect to an AP with the SSID of Connect, and then an ad hoc network with the SSID of Connect (and then an open AP, and then an open ad hoc network).