asterisk users - Dec 2004 - German Howto?

Hello,

I'm a new user of asterisk. I'm looking for a german or simple english
howto, or a description for the following configuration.

City One: ISDN telefonadapter with ISDN and analog devices
                           |
Server with a Elsa MicroLink ISDN/PCF Card
                           |
Connection via VPN or direct, as needed
                           |
Server with a Elsa MicroLink ISDN/PCF Card
                           |
City Two: ISDN telefonadapter with ISDN and analog devices


I've also a SIP account, which I want to integrate.


I want that both cities are able to call each other, or make calls via the
SIP account. The first step I want to try, is that calling our SIP No. make
my ISDN Phone here ringing.

Is this all possible? Thanks for any help or hint
Daniel