As a DA your day off will 98% most-likely not be on Sunday with everyone else. This is a good thing if you want to get out of MacTown. I would recommend finding the scientists who are going down to the ice with you while you are in New Zealand and get to know them. Just mention that you are interested in helping out with anything at all and to keep you in mind. Everyone wants to be a science support helper, but they are hard to get unless your day off is something other than Sunday. Being a dive tender isn’t too hard to become as long as you e-mail whoever is in charge of such events early.
But, do keep in a mind that a scientist cannot take you out of town (Beyond Cape Evans) without a clearance through the Chalet… but those shouldn’t be too hard to get. If you don’t get one, you will be fired and not all scientists know this.
MainBody isn’t a bad time to go. You will be pumped on Antarctica no matter when you go down.