Alright, so you don't have to go what I've gone through, i'll summarize this whole deal.
OZ Instant Messenger is a messenger for your phone that can connect to AIM, MSN, Yahoo, and ICQ. It uses your text messages instead of a data plan (which is why I was looking for it, since I can't afford the data plans available.)
You can download OZ Instant Messenger by going to http://nig.gr/144t
on your phone, and it'll download automatically. You can probably get AIM OTA also, but I had it in my desktop manager after upgrading to 4.5OS. I'm assuming that AIM would be faster than OZ since it uses data, but if you don't have a data plan then don't bother.
Hope this helped.
Thanks to Bastos for the OTA link for OZ IM.