Hi Ricky,
That's a lot of questions, so the best thing I can do is give you some websites for the area so you can pick out the information you need.
Queenstown . Official tourism site.
Queenstown.com
More visitor information
Wikitravel
Experience Queenstown
May will be well into autumn so I would think warmer clothing would be appropriate with perhaps one or two lighter items for any warm days. If you go up into the mountains you would certainly need warm clothes. South Island is a bit cooler than North Island so be prepared for a drop in temperatures.
There is an
airport in Queenstown, so you could maybe fly in there from Auckland if you wish. Or you could fly to Christchurch airport and bus over to Queenstown if you want to go part of the way by bus .