Is it possible to get the Gmail Gchat messenger on the pearl?

go to the Blackberry homepage

http://mobile.blackberry.com

and scroll down. About 2/3 of the way down in the messaging section, you can install Google Talk v2.0. There is also the link to install Yahoo Messenger as well. For other IM services, you need a third party app such as JiveTalk (which will work will all IM services through the one application).