Wrong Character in server name cannot install Exchang 2010

I have been trying to install Exhange Server 2010 on a Standard 2008 SP2.   I have gotten past all of the hot fix issues.  I cannot figure out what to do about the server name.

What will happen if I rename the server so instead of a underline (_) there is a hypen (-).  I read some where that DNS puts a hypen in automatically.  Is this true?

This server is a DC with SQL.  There are only 5 system connected to it.

What will be the repurccesions of renaming the server.

Thank you,