Well, there are a couple ways to look at it:
1. Milk the couple for as much as you can. If they've seen your work from the other weddings you've done and they agree to pay an exorbitant amount, that's their choice. If they're not happy, well, it's not like you have a business reputation to maintain.
2. Ask for what the local market would support. As a frame of reference, I got married in Boston a few years ago. Our photographer was an established pro - not a full time wedding photographer, but she had shot a fair bit more than two, and we saw and loved plenty of her work. She cost us around $2000. (Granted, she is now a more established wedding photographer and is charging appreciably more.) From what I'm gathering of your experience I'd recommend you charge appreciably less than $2000. (Total guesstimage, not having seen your wedding work.)
Okay, option 1 is admittedly snarky. I'm on board with those who think that if you insist on doing this as the primary you are better off charging less monetarily and considering the experience as valuable compensation. But, assuming your skills are up to snuff and you should be charging fair market prices, there are still questions that need to be answered before anyone on here can give you a realistic answer. How long will you be providing coverage? What deliverables are being promised (or expected)? Are you providing X number of edited files digitally, and/or are you providing prints, or an album? All of these (and I'm sure other questions) need to be taken into account.
Whatever you decide, good luck.