XB6 Gateway Questions

I will soon be getting an SB6 gateway as part of a package deal.  I have a few questions.

1.  Can the base IP address be configured?  I do NOT want 192.168.0 or .1.  I need a different sub-net.

2.  Can DNS be configured?  I do not wish to use Comcast's DNS.

3.  Can port forwarding be established?  

4.  Is a manual available other than the brief set-up manual?

Tech Suppport has little information on this gateway so any information will be greatly appreciated.