If you are getting a low voltage shock, then you are not plugging into a grounded outlet. The 30 aml 3 way plug should be plugged into a three plug adapter that will fir a 15 amp house outlet. If your current adapter does not have the third grounding ptong, go an get one. It should look like this...
The otlet on the outside of the traile is just an accessory outlet to plug in awning lights, margarita blenders
, and other such things.
Congratulations on your Airstream and remember to ask lots of questions, no matter how silly you may think they sound.
PS - You may wish to invest in an outlet / cirquit tester. I keep one plugged into the 120V outlet just inside the door. That way I know in an instant if I have shore power and if the circuit is properly grounded.