[otrs] Pointers/Examples on customer integration

Hello all. We're looking to add otrs to an existing system, which contains large amounts of customer information. The customers all have a unique identifier, and I would like to be able to use that same identifier in otrs. Basically, I want to keep our existing customer data in our existing system, and offload the support/tickets/related stuff to otrs. Can someone point me in the right direction to do this? Writing a few modules/components to pull data from our existing system isn't an issue, I'm just looking for pointers of where to start. Thanks.