New Exchange 2010 implementation

Dear Friends,

I need a help for implementing new exchange server in my organization..

In my organization  there are 30+ users are using gmail service for internal and external email communication . My management is planning to implement new exchange 2010 server for the email communication. 

I am new in exchange server. kindly advise me  ,is any domain registration is needed for the same..

Thanks & regards,

Sree.