The "top exhaust vent" is for the G.T.S. (gas turbine starter) this is effectively the engine starter. There should be louvered panels on both sides of the fuselage near the vent, Revell only have depicted this on the port side of the fuselage, it should be mirrored on the starboard as well. Most Hawks are well looked after, but, they do suffer from wear and tear and as they are now approaching 43 years old some wear is definitely evident in the cockpit. As the Hawk has been through Major servicing, most of the airframe would have the "surface finish restored" this includes the cockpit. As such, weathering is up to you and as it's your model and your reference that show this level of wear, who's to argue. I have personally seen cockpits from "Tatty Ton" and "F.R.A.D.U." in this worn condition.
I looked forward to seeing more stunning progress and what can be achieved in 45 days.