To make life simple, use your Apple Care policy. Apple and WN can then duke it out and you will have a new or repaired laptop.

If you did not purchase Apple Care, look at your various insurance policies. While 14 months is fairly far out for accidential damage, it is not unheard of. Credit cards, homeowneres, and the like. These will all require that you have an estimate or a statement that the laptop is beyond repair. Apple does this either at an Apple Store or via its mail in service.

If you have no coverage, file a small claims action against WN. You haven't told us where you live, but I'll presume that it is in California or Tennessee. Both have "customer-friendly" systems and serving a national corporation could not be easier. You will also need your repair estimate or statement for any action. Note that few, if any, courts will award more than the fair market value of an item and that is nowhere near what you paid 14 months ago. However, you do need to go into the matter with eyes open. It is more than possible that a judge would look at this and say that a reasonable person would close or cover the laptop if a drink were being handed over it and that reasonable precautions could have prevented any damage.

Do not use the voucher until after the claim or case is resolved.