How to install mango on your WP7 device with a roll back plan(backup)
Download the 0.02 version (lower on the site), it will automaticly create a backup of your phone (the zune backup process, full rom level of your phone, Read the text file it comes with). You only need the Windows Support Tools installed, not the whole dev package (get at the below link)
Get the Mango update now. Without being a developer. - Windows Phone Hacker
It's so easy, a caveman could do it. Download 0.02+ (what ever the newest version is), Connect your phone to PC and close Zune, click on the Update.bat, follow instructions, it will take a backup of your phone (could take a 1/2 hour or so), then will provision your phone to take the update. After this, check your phone, it will say an update is available, it will install a 7401 update (1 through 9 steps) after it's done, you'll get another message "update is available", then it will install mango.
The whole process takes about an hour to an hour and 1/2. Your current settings, programs, apps, etc are not touched.
Only think to note, save your backup (files are not stored just in the root) or just don't rebuild or nuke your computer, as the files are there.
Enjoy