Hoofin news! Im tying the triple bowline next year. My other half is in the Navy and it was a real challenge getting insurance which I recommend you do.
Definitely tell your HOD to ensure you get the time off!
Are you going to live in a married patch?
Guns is correct that you'll all have to update your wills as marriage will null and void an exisiting will. (Also bear in mind that divorce does not do the same thing so you need to change it on your own)
While you're getting all your documents in order also prepare a POA (Power of Attorney) for things like your personal care should you require someone to make health decisions for you, property (real or personal) and financial. Many a spouse has been caught in the neverending trap of trying to get things done while their spouse has deployed only to discover that without a POA, even the pay office won't speak to them.
Remember to complete a "where is it?" list for your spouse so that he/she knows who to contact in an emergency, list off insurance details for cars, bikes, household, real property, where documents are.
A good idea is also to check out service and trades in your area. Nothing worse than having a pipe burst and not knowing who to trust to come and fix it, or the car, or the TV/electronics while a spouse is deployed or on course. If you can, arrange an account with them to cover any emergency work should your spouse require it while you are away. Saves major aggro on those calls home if it can be dealt with without drama.
For wedding prezzies, ask/suggest for things like a subscription to the RAC for car emergencies, a safety deposit box in a bank or a fire proof box you can keep at home, ask for a year's home insurance coverage as a gift, or even prepaid legal fees to get a new will drawn up.