I have a mogul and here is what i know. Windows Mobile is highly customizable. At the moment though, the touch pro doesnt have to much that you can do with it (seeing how it is brand new). In a few months however, you should be able to install custom roms (like an operating system, but different versions of the same base (windows mobile)). As fare as face book there are a few applications. 2 here:
http://forum.ppcgeeks.com/showthread.php?t=31417. For aim there are various apps like "Slick" (look it up) and the classic app just for aim at the bottom.