I'm not sure there is an official script for such ceremonies.  I've personally been involved in organizing four Medal of Honor related events and have attended others.  I offer the following suggestions:

See if the Governor or Mayor is receptive to signing a declaration making the day officially Sgt ________ (name of recipeint) Day.  If the answer is yes, one of the guests at the ceremony can read the proclamation during the program.  Perhaps a former commander or unit member, depending on who is invited to assist in the proceedings.

Ask the local VFW, American Legion or National Guard to provide a Color Guard.  They can then coordinate the Posting of the Colors and the National Anthem.  Sometimes, the Pledge of Allegiance is fitting as well.

One such ceremony I helped coordinate had the local Navy Reserve pipe in the VIPs in addition to handling the Color Guard duties.  The Recipient was obviously a former Sailor.

Have somebody read the biography of the individual prior to the unveiling.  

Depending on the situation, I've also seen opening and closing prayers.

I hope this helps.