1 - Does Ensim webppliance 3.0 runs under Red Hat 7.2?

2 - Installing Ensim webppliance 3.0 will delete PHP, MySQL,..., if i have them already installed, or it simply install the GUI.

Thks in advance...

1) No, though they will be releasing a new version in about a month that will run under RH 7.2.

2) It does delete some of the modules on your server and replaces them with modules to do the tasks that have been written for Ensim. I don't know if PHP and MySQL are 2 of these modules, but I know progresql and postgresql are.