Oh, I am worried about some of the advice here. I would not hit her double-barrelled with the UN fiasco or anything like that. Full-frontal attack on a JW usually results in a Cognitive Dissonance breakdown, and suddenly you become the devil. If you want to gently, gently guide your wife out, here is what I advise:
1. Get Steven Hassan's "Combatting Cult Mind Control" http://www.amazon.com/exec/obidos/ASIN/0892813113/104-6371983-4274349
2. Speak in a mild-mannered tone at all times when talking to your wife or the elders. They are programmed to respond to "mildness". Also, any anger or vicious speak is immediatly labelled as satanic. You don't want to grow horns.
3. Find out what your rights are as head of the household. Mildly ask to exercise them.
4. Don't directly oppose your wife's desire to get baptized, but do what you can delay it. For instance, you may ask to be there for her her baptism, but before doing so, you would like to interview an elder on what commitments is required of a JW. You could probably drag out three or four meetings at least. JW's expect you to be resistant to the amount of time away that the WTS requires. The Secret to Family Happiness book advises the Witness partner to be patient and accommodating. Find out what kind of accommodations your wife is permitted to make to be available for your needs.
Is there any hope?
It all depends on your wife. How deep is she? Is the watchtower society meeting a deep need she is not getting filled elsewhere? Are there alternative societies or groups that would meet those needs better, if she had enough exposure to them?
How many years am I going to lose here?
Let's see. I am going on four years. This is not an instant process, if I do manage to be successful. You can PM me for more tips if you like. I don't like to publicize all my "tricks". For the long term, find a way to be open and honest with your wife about your feelings, without directly threatening her faith. Like all successful relationships, there has to be honesty. My hubby knows, for instance, that I frequent this board. The balance, I think, is not to freak out on your partner, but also demand respect. Mildness, mildness.