You've already gotten some great advice! I think you will enjoy the 50mm, it's one of my favorite lenses for weddings. Definitely find a back up body to use, even if it's just for the day. If you decide to stay film bring more than you expect to use and bring a ton of extra batteries.
As for the other parts of the wedding, shooting for a family member isn't always bad. The first weddings I did were receptions for friends and family. Make sure you know what style they are looking for (posed, candid, etc) and make a list of their must have shots to use as a reference for the day. Also, do an engagement session with them to practice your skills and see how they photograph. I've learned a lot about my couples during this time. For example, a bride might bite her lip when nervous, or the groom might nearly close his eyes when he smiles. Knowing this beforehand will lead to better results at the wedding.
Also, check with the location where the ceremony will be, if it's in a church or other place or worship there are often guidelines about the use of flash (many won't allow it) and where you can stand during the ceremony. Make a visit to both the ceremony location and the reception location and take some test shots.
As for film vs. digital...that's your call. However, make sure that you are comfortable with whatever camera that you choose.
My standard gear for weddings includes the following (but remember that I do quite a few weddings a year, so not all of this is needed)
-Canon 10D
-Nikon D70
-50mm
-100mm macro
-20mm
-70-200 f2.8 IS
-4 sets of rechargable batteries + quick charger
-3 extra batteries for each camera + charger
-Softbox for flash
-Quantum flash + bracket
Also, come check out the Portrait/Wedding section in the galleries, you'll see examples of work and some good tips as well.
Good luck, have fun and post photos when you can!