From the Java Control Panel Update tab, you can manually check for an update any time by clicking on the Update Now button located at the bottom of the Update tab on the Java Control Panel.
Java Update can only be run if the system is connected to the internet.
For daily updates, you can select the time of the day for the update.
For weekly updates, you can select the day of the week and the time of the day.
You should leave this process running in order to ensure getting the latest secure Java version.
Yes, updating to Java 7, using Auto Update or updating through the Java Control Panel, will remove the highest version of Java 6 installed.