There's no migration path as in "do these 2 steps and you're set". Best thing is to start from the database schema and generate the DAL, then modify his client code to use the LLBLGen DAL.
So reverse engineer the database to an entity model (select LLBLGen Pro runtime framework as target framework) see designer documentation, or the entity framework video we have on our site which takes you through the steps, it's for Entity framework but it illustrates a lot of the points), then generate code for selfservicing as that comes closest to entity spaces.
Then unfortunately you've to migrate your own code which uses entity spaces to make use of our code. I don't know how much code this is though...