Where are you in the SE? Just curious.
We have a shop sponsored team as well as some other sponsors on board. The perks for a 5 are pretty much limited to race reimbursements, shop, and sponsor discounts. As for training, that's really an individual thing. Group rides are so you can have some company on a ride. Really nothing structured except for the occasional rotating pace line practice. This time of year things are very unstructured anyway as it's a base and build period for the spring races. No need to over do it right now.
For advantages in a Cat 5 race, there aren't any other than you may know someone else in the race. Cat 5 races aren't tactical events.