The easiest way to change the IIS site id is to create a .bat file like this:
(Assuming that 1135282223 was the id of your current site and 5 was the ID you’d like to have)
CSCRIPT %SYSTEMDRIVE%\Inetpub\AdminScripts\adsutil.vbs STOP_SERVER W3SVC/1135282223 CSCRIPT %SYSTEMDRIVE%\Inetpub\AdminScripts\adsutil.vbs MOVE W3SVC/1135282223 W3SVC/5 CSCRIPT %SYSTEMDRIVE%\Inetpub\AdminScripts\adsutil.vbs START_SERVER W3SVC/5
What is %SYSTEMDRIVE%\Inetpub\AdminScripts\adsutil.vbs ?
It is a ulility included in IIS.
List of utilities included with IIS can be found here