I have looked around and haven't found anything concrete.

Is there any tutorials on how to show/hide a form or textbox based on if a value is selected.

I have something like this Dropdown box with (Add, item1, item2,item3 ect..)

if add is selected show a form to add add with some attributes such as (First Name, last Name ect..) else it will just do an action with the selected item.