(when you attend your wedding everyone shows up, someone falls to the floor dead)
I
hate when that happens.
Go to the temple of Mara in Riften and talk to a priestess (I forget her name) she will send you on a few Dr Phil missions all over Skyrim. Once those three missions are completed she will give you an amulet and unlock its power letting other NPCs take notice and giving you new dialogue options.
Nope. You only have to talk to Maramel (the priest) about marriage and ask him if it's possible to have a wedding in the Temple. You can obtain the Amulet of Mara from any source, you don't have to buy it from the priest, or do any other specific quest for the Temple. I've usually found 2-3 in random loot by the time I get to the point where I'm thinking about tying the knot, I just hang onto one until I'm ready to use it.
Once you've talked to Maramel and have the Amulet, go find the person you want to marry and equip the Amulet. If they are interested in marrying you (read: you have fulfilled their requirements, usually the completion of a favor quest or in the case of some NPCs, an entire questline for their faction of choice) they will remark on the fact that you are wearing the amulet. Let the conversation progress until you have agreed to the marriage. Then go back to Riften and tell Maramel that you want to arrange a wedding in the Temple, he'll do all the work from there and all you have to do is show up the next day within the specified timeframe.