Upgrade ehcp from previous versions

There is no automatic way yet, unfortunately.

Manual way:
if ehcp database structure has not changed, you should simply copy new ehcp files to your server.. you dont need to run install again, mostly,

if you want to run install script again, dont forget to backup your database,
install script deletes all old data by default..

you may then restore your backup...

if ehcp database structure (little chance) has changed, the best way is to recreate all domains by hand, after new install...
or i should write an upgrade script for you..
this case is very rare... since ehcp database structure is not changed most of the time, (between minor versions..)