Freezing I would also recommend two bodies, nothing worse than damaging your camera in the middle of a wedding and not being able to get any shots, I would beg borrow or steal another one as an insurance policy. Also that lense you are using is pretty slow, for the shots inside the church you want something fast f2.8 is probably as slow as you would want to go, see if you can borrow something faster, a 70-200 f2.8 makes a great church lense, if you are using a flash make sure it's not the pop up and bracket everything, take as many shots as possible. I shoot jpeg (more shots per card less processing time), bracket shots and take as many as possible, last wedding I went to I shot about 1500 images.

You have to come prepared, backups for everything, nothing upsets a bride more than seeing crappy photos after the event. I've shot at 3 weddings for family and friends and it's difficult and nerve wracking, but can be a lot of fun if you are confident in your abilities.

When taking the family/group shots start with all the guest (big group) and work your way down to the bride and grum. Its much easier to get all the guest to gather around, than to shot smaller groups, one at the time with members missing high and low.