A lot of answers are focusing on the wedding and maybe that is what you were looking for. If so, feel free to ignore my 2 cents below. I'll offer just a few thoughts on what happens after that day.
1) Marriage is nowhere near as life changing as having kids is. So if kids are not in the picture, you should be fine. If kids will be in the picture, that's when things really change.
2) Sex, finances and family are all important discussions but most folks considering marriage have at least talked a little about those. Try and be in sync on those before tying the knot. That being said, division of labor is one discussion that is rarely discussed in advance (e.g. who is going to do what in the marriage). Make sure you are at least in the same ballpark on that as it can be a resentment builder
3) Sometimes the smartest answer is saying nothing at all. Especially in the heat of an argument.