First DC , FQDN/Domain name selection

Hi,
I installed the first domain controller allocating the root DC and we have already a domain name as some xyz.net and the domain provider is used in controlling the DNS settings like hosting.com and the process can be described as when anyone enters the address is also used in hosting the Domain name provider.
Later I made use of MS Exchange 2010 in the domain environment other than using the hosting company which is provided by using the mail service and it has many types of limitations so the main theme is that If I make use of xyz.net on root DC for FQDN then some necessary steps needed to be taken in eradicating this and even the site must be hosted if I no need the web server.
I have 2 multiple branch offices for joining with the domain in pointing to the root DC’s or IP constantly. So please provide me in solving this issue. Thank You.
