Questions about a new setup, new to asterisk

Hello, I am new to asterisk and have just installed asterisknow. I would be interested in using asterisk in my office but would like to have some suggestions as how you would configure our set up. If this is going to be costly it probably wont be deployed so keep that in mind when making your recommendations.
We currently have:
Asterisk Server
4 vonage lines (3 voice + 1 fax)
2 Google voice lines (not in use at the time)
Several skype accounts (each person a separate user name)

What would be ideal is if there was 1 phone # which people called in for wholesale and from there they had a prompt for separate extensions and a different phone # which is for retail customers without prompts. Then depending on the prompt it would ring either one of the office phones or a softphone or skype phone.
Our phones in the office are standard phones (not sip phones) and are connected through the vonage adapters.

On a separate note is there any way to connect skype to asterisk for free? the digium solution costs $66 per concurrent line.

Thanks in advanced,

Does vonage pass you the number that was dialed? You should be able to do different things with each incoming number by treating them like extensions in your dialplan.

[code][context for incoming vonage calls]

exten => +2222222222,1,Goto(somewhere…)

exten => +1111111111,1,Goto(somewhere else…)[/code]