In my most deepest, honest opinion: dont do it.
Some couples are just better off not getting married. My parents are divorced, and now they are in a relationship with someone else. Only this time: they dont intend on getting married... again.
I for one dont believe in it: given from what I have been through with my parents. I learned from their mistake, and others as well. I'm sure you love your girlfriend, and you want whats best for her. But consider this:
Is it really quite necesary to throw a huge freakin' party to announce to the world that you're crazily in love with someone? And even after the marriage: things WILL get tough between the two of you. I'm sure you dont want that for your girlfriend.
Now that i've said my piece, I'll shut up now -.-