I shot 2 of my sister's weddings as a gift, and got some paid work by doing so. For one of them all I had was a D800 with a 35mm 1.4 and 85 1.8, I never felt I needed anything extra - bar a second body! I would never do that again! For other weddings I made sure to have back up, I borrowed an extra body and I had more lenses too. I also had a flash for each camera. The first wedding was stressful, I was really anxious before starting, but by the time the church ceremony was over I was flying, I started to really enjoy it. I had looked at hours and hours of tips for shooting weddings beforehand and it did come in handy. I had done a bunch of portrait shoots in the past and I think that helped also, I kind of broke the day down into mini portrait sessions in my mind. The morning prep, pre-church shots of people arriving, a lot of candids here, the ceremony itself, more candids pre-meal at the hotel, the group shots with bridesmaids and groomsmen - I took them away from everyone else to get these done quick and painlessly, the post-meal speeches, the first dance, and then fun shots of people dancing. One thing that i found really helped was to make a shot list, all of the shots I wanted to nail I made a list in order of timeline and I checked this throughout the day. I was really glad I did so. I talked to the brides before the day too and asked was there any specific shots they wanted, anything out of the ordinary, like some of them wanted shots in the wedding suite, others wanted an overhead shot from the church balcony as the couple were leaving, to get all of the guests in, some may prefer you to get them leaving the church if there is a confetti party waiting, one wedding the couple released doves outside the church - I had to plan ahead for the balcony one, had to get the caretaker at the Cathedral to open the balcony up for me, and I needed to be up there before the couple walked down the aisle, I had the one chance to get this right, thankfully it worked out fine
Hope all goes well for you