Follow the upgrade instructions @ vtiger.com. It should do all the necessary db conversions etc. There may be a few small differences that I can't remember now. Click to dial works but may need a few tweaks. You did backup didn't you?
Try this. It wasn't easy to find. I think the one I used was easier. Maybe Bob will put up a tutorial on elastixconnections.com. I think I remember he posted some notes in one of the mailing lists or something. Maybe someday there will be an rpm too.