After you accept it, the NPC will urge you to set up the wedding ceremony immediately and you'll have a pretty unromantic story to tell your future children about how you proposed. If there is a relationship to foster, you'll get an additional dialogue option asking the person whether he or she is interested in you. Typically this interest is indicated by verbal cues such as, 'It's a nice day when you're around.' Many NPCs will require you to complete a specific quest before they will fall for you. With the Amulet of Mara equipped, simply speak to an NPC that has previously expressed some sort of interest in you. Congratulations, you're now ready to put a ring on it! Well, an amulet at least. Push the query further to receive the option to purchase the Amulet of Mara from him for 200 gold.
YES NOOnce you meet Maramel, ask him to be enlightened about Mara, the Goddess of Love.