Chimps,
Depending upon who the company is, will depend on the level of training they will provide you to transition to a multi-crew turbine aircraft. My advice quite simple. You will have a lot of new concepts and equipment to learn about so dont waste your time with generic stuff (like what you studied in your ATPL theory days). Aircraft systems and performance etc should be adequately covered during your ground training. New equipemt would be worthwhile reading up on, EGPWS, RADAR, TCAS etc, but make sure it is the same equipment that is fitted to your aircraft as they can be different. Also if you can get hold of the SOP's, read up on things like standard callouts and aircraft configurations and speeds etc used during instrument approaches. The advice I was given before commencing training on Brasilias and then later Dash 8's was dont worry about pre-study, enjoy the break leading up to the new job, but be ready to study hard once you get started!!!!!. In hindsight good advice.
Good Luck im sure you will enjoy the challenge!!!