Upgrading eclipse on Mac

On my Mac, I am using Eclipse Galileo. Recently I noticed Helios is available.
How does one go about upgrading? I downloaded the .dmg. Do I just run it? Will I end up with two versions of Eclipse or will it sense and upgrade the existing version?
Or do I just delete the old one and run the .dmg?

Of course I know I can try it out instead of asking stupid questions, but I got some plugins installed and I am trying not to reinstall them.

A dmg is a disk image. Usually it will contain either of an installer (which you would run), or the complete application (which you just copy to your /Applications folder).

You don't want to run out of the dmg -- it's just temporary and you should delete it when you are done copying or installing.

My brain is zonked nowadays.
It is a tarbell and not a dmg. So sorry.
I extracted it and now have a choice of launching Galileo or Helios. On to installing the plugins I want.