How do I know for sure IF I have Java 6 (from Apple) installed as well?
Triple-click anywhere in the line below to select it:
java -version | open -f -a TextEdit
Copy the selected text to the Clipboard (command-C).
Launch the Terminal application in any of the following ways:
☞ Enter the first few letters of its name into a Spotlight search. Select it in the results (it should be at the top.)
☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.
☞ Open LaunchPad. Click Utilities, then Terminal in the icon grid.
Paste into the Terminal window (command-V).
A TextEdit window will open with the output of the command. If it contains this text:
java version "1.6.0_51"
Java(TM) SE Runtime Environment (build 1.6.0_51-b11-456-11M4508)
Java HotSpot(TM) 64-Bit Server VM (build 20.51-b01-456, mixed mode)
then the latest version of the Apple JRE is installed. Anything else, it's not the latest version, or not installed at all.
And would this Java 6 update affect my Java 7 install in anyway?
No. They're completely independent of each other.