RCT Pollard.
The 506th uses the ACE3 basic medical system. When you graduate from OSUT, if you want to become a medic you can declare a 68W (Medic) billet if there is one available. As of this moment, there are no Medic spots available in the unit. You will then need to take Combat Medical School where you will taught more in-depth about the medical system, proper tactics for casualty recovery and other skills you will use as a Medic. After that you will be assigned to a squad as their Medic for training and operations.
If there are not any 68W billets available when you graduate OSUT, you can take any other billet that is available and when a Medic billet opens you can request a transfer into a Medic billet. I'm not sure what you mean when you ask if Medics are, "specialists". If you're referring to rank in the unit, as SPC Salvatore said you start off as a private and work your way through the ranks with time. Squad Medics are rank capped at the Specialist (Corporal) rank and Platoon Medics are rank capped at the rank of Sargent.
Hopefully this answers your questions.
SSG M. Brewer
Company Senior Medic
Combat Medical School Chief Instructor