Not much advice to add to the above really. 14 hours work without any guarentee of payment for either your time or work produced is high risk though. Can I ask why the original photographer pulled out? I've been doing weddings for a while and have never had to pull out so just curious really.
Do the picture viewing at home and do not let them leave with any photos. Sit them down and take them through their choices.
For a first job, and particularly for the hours put in, I'd aim to be around £500+ clear as a minimum. 14 hours is effectively two days work so should really be nearer the £1000 mark to remain competitive. Plus your costs prints, album, post production time, travelling costs etc.
For the future take a deposit. Some take only 10%, which is too easy imo to walk away from. I take 50%, this sorts the wheat from the chaff for me. On two occassions in my early days I took a 10% only for the couple to turn around when the balance was due 28 days before the wedding and say Uncle Fred had stepped in. They lost £100 but I lost over a grand without any hope for a booking on that date.....so it's 50% down if you want to book me and it is non-refundable (discretion is wise here in the case of serious illness for example.)
Price your product for the market, with a view to increasing your prices as the value of product comes in to more demand.
