A lot would depend on the lighting conditions at the ceremony. If it is practical and you can gain access a few days before the event, visit the church and test your equipment and skill in getting good photos in that setting. Many churches do not allow the use of flash during a religious service, so be aware you may have to use existing light. Take a volunteer model if possible.
Take plenty of photos before and after the actual ceremony. Try do do these in more ideal lighting conditions. These will help fill out the ceremony if your keeper ratio there is not as high as you would like.
Just because you are in poor lighting doesn't automatically mean you should use the widest aperture on your EF 50mm f/1.8 lens. Stop down enough to get enough depth of field to include everything you need to be in focus.
While noise from using a high ISO is not desirable, it is better than blur from too slow a shutter speed. Shoot at the ISO you must to get the shutter speeds you need and deal with the noise in post processing.
Save your photos as RAW files. You will have much more latitude to adjust White Balance and Exposure in post processing. In a pinch you can also under expose a stop or so and then push the exposure back up in post.
Use the correct metering mode for the shooting conditions. Evaluative works well for many situations, but if there is a large difference between your subject and the background, consider using partial or even spot metering if available on your camera.
If the lighting conditions are beyond your gear's capability, consider renting a high quality lens. If the EF 50mm f/1.8 is not the focal length you need get a fast lens that is. If there is no camera specialty store in your area that rents lenses, try LensRentals.com or borrowlenses.com. Both are reputable and offer fast delivery when needed. The earlier you order, the better the shipping rate will be.