only administrating part of server is web based, you can use variety of clients to connect to it (standalone, java, web based, flash, etc.)
IIS should work fine i think. Do you really need it for your IM server?
client starter guide? Hm… Start Admin Console and create a user, Download Exodus, install it, run it, register your user in it and connect to server. In Exodus account setup you should put: username@servername