Rename Domain controllers !

Dear All,

i have on my production a Domain controller 2k8R2 and Exchange 2010 running,

my Domain name is Domain1.lan and my exchange is configured to send emails using ...@domain1.com however there been some changes inside the organisation and i have to change the domain1 to domain 2 and also my exchange too,

from Domain controller side, how can i do this? should i  decomsse the DC ? should i rename the DC ?

please advise the correct steps to do this.

PS: infrastrcutruur on DC is for 4 peoples.

thank you