NEED HELP Before EXPENSIVE Gown Is Ruined

I need help understanding alterations so I can figure out if this alterations person knows what they are doing. This is a pre-owned gown that was originially $1800, with a semi-long train. ---Can it be shortened just in the front, and then adjust the bustles for the back? Or does it have to be shortened all the way around? (This dress will need to be shortened about 4 inches). THANKS!