Persium: Shipping from Arda should be more than $10. I think I paid $8 on my last wig from them.
For wigs, you should be able to Google around for a bunch of wig wearing tutorials, but here are the basics:
Since your hair is so long, you should pin curl it up.
Then put a wig cap on over it. Wig caps are essentially panty hose for wearing wigs. They keep stray hairs from slipping out from under your wig and becoming visible.
Use hair pins (that's a specific kind of pin, not just any ol' pin that goes in your hair) to keep the wig on your head. Bobby pins right in front of your years, and at the front or back will keep it from slipping around. Whether or not you put them on in the front or back depends on where your wig is heaviest. If you've got a big bun or ponytail in back that wants it to pull the wig backwards off your head, you'd put bobby pins at the front to keep it from sliding back.
Also, not wig related, but you should really wear makeup! Even the very basics, like foundation and eyeliner, will make you look much nicer in pictures. It'll keep your skin looking even, and if you start to sweat (Kumoricon is still a summer con, after all) it'll keep your face from getting shiny from grease. I guess eyeliner could be optional since you're being Dave, but if you ever want to take your glasses off, it's important that your eyes don't disappear in all the other big, heavy and bright stuff you've got on.
