@dadpad,
So dadpad, what do you want to know? Is your wife going through menopause? If so, you need to do some reading- btrflynet's links were good--and talk to your male friends seriously, don't get into that male type of joking which makes serious discussion impossible.
Menopause is tough, for women especially, but men come in a close second. Talk to your wife and let her know you genuinely want to help (and that you genuinely need help).
You seem like such a nice guy that I really think that you and mrs dadpad will come through stronger than before.
One additional note: if you kids are feeling the effects, do include them in discussions. It might turn out to be one of those discussions that. when you look back, truly mattered for all of you as your family changes and the kids are maturing, able to understand and appreciate adult matters. This could be the time when your family can speak to each other like adults, with understanding and empathy.
Since I don't know what you or your wife are going through, please let me know. I'm not going to get indignant, I do want to know if I'm on the right track.
Good luck, you aussie, you!