I'll never totally understand parents. I could get an A on a report and they'd wanna know why I didn't get an A+. Go figure. I wish you good luck in dealing with the situation. At least you have some options.
While the maid of honor is traditionally female, traditions are changing all the time. If your friends are OK with it, and you are too, then I say go for it. Maybe traditional terminology could be modified a bit so that there's a Best Man and a Man of Honor? How would you feel about it if you were the Man of Honor?
How large is the monitor, who makes it, and how old is it? Was there a photo of it on Ebay? What kind of rating does the seller have? I've seen deal like this turn out fine and have also seen them turn out bad. I'll keep my fingers crossed that you get a good deal.
~gary.