Information Request

Does anyone know the rules on leaving an airport during a connection? Believe it or not, with all my travels, I've never done this. But I have an upcoming flight which may stick me in Shannon, Ireland from 10am to 4pm and since I've never been to Ireland before I thought I'd skip out and take a look.

So does anyone know:

a. Do I have to claim my luggage?

b. How big is the Shannon airport?

c. anything about Limerick or Ennis, Ireland?

(no subject)

Well, forget about Ireland. My work changes their mind every two minutes.

ETA: Thanks everybody for your great advice! I will save it for next time!