Exchange 2010/2013 to Exchange 2013 CU9 Migration

Hello All..........I have an environment where I have Exchange 2010 SP3 across three-3 sites.  There is also Exchange 2013 CU6 at the Primary site that is also the site which is internet facing.  I want to do following:

1.  Install Exchange 2013 CU9 at the Main Site with Two-2 MBX and Two-2 CAS

2.  Install Exchange 2013 CU9 at other two sites with Two-2 Servers (MBX and CAS combined)

Questions:

1.  Should I take it as a normal installation and configuration for transition or there is something that I need to take into consideration?

2.  Is there any step by step article with that regards which can be helpful in creating such an environment?

3.  Would I need to run Forest and Domain Prep?

4.  I would be building IP-Less DAG between Sites, so any guide with that respect would also be appreciated.

Thanks in advance.