ok, here it goes...from the dev network, on the main server, go into "user manager for domains". Next, choose policies at the top of the page. A gray menu box pops up. Choose "Trust Relationships". Two white boxes appear. The bottom one, trusuting domains must be filled in here. Click add, then type in the name of the domain, enter a password that is valid on the other domain and confirm it. Click ok.
On the production domain, go through the same steps as above but for them, the top box must be addressed. In this case, you fill in the name of your dev domain. The password that is used in both instances is one that is agreed upon before this is implemented. This is not a users or administrators password, this is a password established to create the trust.
In reference to your second question, the trusted domain is the one that is allowed to access your resources, you trust it. The trusting doamin is the one that allows its resources to be accessed, they are trusting you.
Good luck!
Mike