don't you want to look like yourself on your wedding day? i wouldn't risk it. department store make up artists can be scary, believe me. i wear almost no make up now (nothing, or mascara and maybe tinted moisturizer). when i was younger, i loved doing my make up. i would just sit in front of my mirror and do it over and over . . . i was bored, lol. my mother and i would get makeovers in department stores (just for fun - we'd just ask if they wanted to do it, if they were having a slow day) and as "models" for students at the aveda school. we'd usually buy something in the department store, and at the aveda school, we'd get a gc to the store. anyway, my point is, sometimes it was fun, and sometimes it was SCARY.
i really recommend going to a good department store make up counter (make an appointment if needed) and saying that you are getting married soon and want natural looking make up because you normally don't wear any, but want to when you get married. ask them to do your make up and to explain everything as they go. then buy some stuff and start using it for practice. i would buy the foundation from the department store. mascara, eye liner, eye shadow, whatever . . . that stuff doesn't matter as much and you really can buy it for cheap at the drug store. it sounds like pp's suggestion of MAC could be good. my absolute favorite make up counter was yves saint laurent (which we went to at saks) and they would give me a drawing with a face on it, which they applied my make up to and wrote down the names and colors of everything they used in case i wanted to buy it later. it was awesome, but i think pretty much anything is fine - the person matters more than the quality of the make up. oh, and if you don't like the results, then try again somewhere else.
if you are remotely artistic, then i think the suggestion for drug store make up and internet tutorials (or instructions from a friend whose make up you like!) would also be perfectly reasonable. oh yeah, i've been married twice and did my own make up both times.