I don't know if you want to use the VPN connection that you have, VPNs are usually used for secure transmission and data integrity for applications.
If you want to create a Trust between two Domains give this a go:
On each PDC on both Domains you need to use User Manager For Domains, get someone who has Admin rights on the other Domain to open up User Manager For Domains.
Remember this:
The domain that holds the resources that need shared is called the Trusting Domain, the domain thatneeds access to the resources is called the Trusted Domain.
Setup the Trusting Domain by clicking Add in the Trust Relationship box, then setup the Trusted Domain. NT desires passwords for Trusts to be established which are only used once the other person on the other PDC will need this password to perform these steps in the other Domain, you can use the net send command in DOS to transmit the passwords, saving you from sitting at the phone.
Once the Trust has been setup the Trusting Domain then needs to know what user(s) needs access to which resources, find the resource that needs shared, created a new Global Group with the appropriate users and permissions then use User Manager For Domains to set the correct permissions, you willsee in UMFD that the drop down box at the top when selecting the Groups or users will now work and the other Domain will then be present, you can then choose the groups or users from the other Domain and add them into this new Global Group (which should then be placed into a Local Group then the rights assigned, UGLR rule).
Once this has been done the user in the Trusted Domain should now be able to gain access to the resource required.
Hope this points you in the right direction.
