Hi Annette!
FRB is "Flat Rate Box." The post office has flat rate boxes for all over the U.S. and large ones specifically for our soldiers overseas. The rate is now $11.95 to send a fairly large box. You can pick them up at your local post office or order some online from the USPS website. The boxes are free. You just have to pack them, and despite what they weigh (pack 'em tight!) the post office will ship them for that flat $11.95. It's a great way to save money on shipping so you can put more items in the box! It is considered domestic in terms of shipping but international as well, as they will not take it without a customs form (also available at the post office). I don't know if insurance is even available on those boxes.
As for the cases of soda, do what you think is best. I find that I can ship liquids without a problem in those flat rate boxes as long as they are well wrapped. If you want to try to send them the way that the bottling company packed them, go ahead. I have a very good feeling that it will be VERY expensive, however.
As for the Valentine's Candy, is the candy inside the bag individually wrapped? If so, it's ok to take the pieces out of the bag. If not, leave it in the bag. I bought some that included little cards and heart shaped candy that went on them, and since the candy was wrapped, I opened it and filled out the "To:/From:" bits and mailed them over.
Good luck with your mailing! And feel free to ask any more questions you might have!
Amy