Leaping into the unknown!

Hi Guys, after a lot of head scratching and slow progress I just wanted to see if I could get some advice and guidance.

I work for a company with About 150 users.
There are 2 separate domains/forests in 1 office.
Soon to be adding a satellite office within the next month or so.

The plan so far is to create 1 new domain/forest that will replace the old ones.
However, I have never created a server from scratch before let alone all the bells and whistles that go with it.
I have an IT consultancy working on some possible solutions at the moment but just wanted to understand a little more about what's involved ...

As far as I'm aware, the following need to be in place after the change;
DC with AD DS, DNS, DHCP, file and print services
Exchange server
SQL server

And at the remote site I'm thinking of having an RODC as there will only be about 6 people there, They will need access to emails but will be working on there own set of files and data so no need for DFS or the like.

Any suggestions about how I would set this up would be great?
*Thinking out loud*
*Do I need more than one DC?
*Do I need to take into account any special considerations with using Exchange
*Do I keep file and print services on a DC (or even together)
*Are there any advantages to having a separate domain for the satellite office
*Any links to any tutorials? walkthroughs?

Cost isn't so much an issue but having a smooth transition between systems is!