Yes you can upgrade for free. I never used 4.3 so I cant tell you what the benefit would be but I'm sure you would be happy. Get it here http://forums.crackberry.com/f52/new...nguage-236552/
I also suggest you look at the link for proper upgrade/downgrade procedure to familiarize yourself with the process.
It seemed to go OK, but at the end of the Application Loader Wizard I got the the following warning:
"Warning: After completing the loading operation, you must activate your device wirelessly to continue to send and receive messages and use other Blackberry services. If you do not want to continue with this loading operation, press Cancel."
It took about 30 min or so (I didn't time it, but it took a WHILE), and after it was all done, everything seems to be working great. Checked email, IM, and a few other apps.