Air rushing through the big flat thing (aka the plenum) is normal.

As Rob says, paper clip test is your starting point. each code repeats itself 3 times, so you dont miss it.Sequence begins and ends with code 12.
So - start of sequence is one flash-pause- two flashes.This happens 3 times, so you have just seen code 12 three times.The same thing will happen at the end of the sequence.
If you have for example, a code 19 you will see code 12 three times then one flash - pause- then 9 flashes (again, this will display three times) then assuming code 19 is the only fault code you will get code 12 (3 times) to end the sequence.
Spend a little bit of time sat in the car with a pen and paper writing down what you see, as number of times light flashes and it will probably become clear after a while.
It can be a little daunting the first time, but like most things, once youve done it once or twice it becomes easy.

Hope that helps, rather than causing more confusion.
if you still dont get it , dont be afraid to shout out again.We were all complete beginners once.
