Thank you for answering, vertugarde, sorry, I don't know your name. You are correct of course!
The dress was actually a gift to her from the MGM studios.
It was donated by Princess Grace to the Philadelphia Museum of Art. It is not presently on view, the last showing was in May of 2006.
Grace Kelly was still under contract to MGM for 7 more years at the time of her marriage. She agreed to the wedding being filmed by MGM for worldwide distribution in order to be released from her contractual obligations. Later on in her life she had regrets about this intrusion into her private life.
The actual gown was made from antique Valenciennes rose- point lace. There were over 25 yards of silk taffeta and 98 yards of tulle. The veil was covered in thousands of seed pearls and appliqued lace lovebirds.
...I remember the fouferah surrounding the wedding. There was more publicity than the Second Coming.