Much, much easier than you think... follow these steps.
READ THIS FIRST
1.This is a DEVELOPER PREVIEW BETA 1, expect the bugs, etc.
2.You don't need to jailbreak the device, and the jailbroken device will lost its jailbroken state.
3.Backup locally if you want to. (Normally iTunes will do it for you.)
4.Either of iPhone 4 or later, iPod 5th Generation, iPad 2 or later is required.
1.Download the regular iOS 7 ipsw from websites. I won't give the links, you must find them on the internet. The correct file size should be about 1GB. Make sure to select the iDevice model that you're using.
Guide : Torrents can help you.
ipsw name example : iPhone3,1_7.0_11A4372q_Restore.ipsw
2.Open iTunes, and then SHIFT+CLICK at "Check for update" (or ALT+CLICK in mac)
3.Select the downloaded ipsw file
4.Update, the process doesn't take a long time. (5-10 minutes)
5.The device will restart, and you are free to use all the features and the Developer UDID isn't required in this method.
HAPPY iOS7-ing !