great pic that, really up close
there are only a couple of parts in the, the pipes going in and out, the valve and the matrix itself. My money would be on the valve, the matrix is aluminium not like the crumbly engine rad.
From the position you are in at the moment (with air cover removed) you can see a cover made of black plastic, remove that and you should be able to see the offending parts, its only a couple of screws, but you may need a stubby screwdriver IIRC to get it off, a bit fiddly but OK with the right tool.
The airbag is best tackled by disconnecting the battery and leaving for 30 mins, it need not be disconnected as the wire is about 2 foot long, enough to happily sit on the floor, but may be better out of the way seen as you will be there a while.