When it comes to OCing in a bank, you shouldn't worry too much. I haven't OCed in a Navy Federal but I have in a number of others. The only advice I can give is to be aware of how you could be perceived. I you look nervous, it will make them nervous. Take your hat or sunglasses off before going in. Smile and say hi to the first person you see. This will put the bank folks at ease for the most part.