Help needed

I'm going to a wedding on October 1st. It's a Friday night- 1.) what should I wear, dress or suit 2.) where should I look for it? I live out in Eastern Suffolk, so it's either Smithhaven Mall, Estelle's or mail order! Help, please!

Dress Black-Smithaven Mall should be fine
Where si the reception if you don't mind me asking

The reception is at the Majestic Gardens at 7:00 pm