We should consult the Bible on this question, as with any other matter concerning faith.
In 1 Tim 2:12, Paul, by inspiration said, "But I suffer not a woman to teach, nor to usurp authority over the man, but to be in silence."
The way I understand it, the position commonly referred to as a "pastor" is one of authority, correct? If so, then a woman would not scripturally be authorized to serve in this capacity.
Also, "pastor" is another term for "elder", or "bishop", right? According to 1 Tim 3 and Titus 1, one of the qualifications for one who serves in this capacity is to be the "husband of one wife". No woman can be that.
Concerning a woman preaching, when we preach, we are to "speak as the oracles of God" (1 Pet 4:11). We are to do all, in word or deed, in the name (by the authority) of the Lord Jesus (Col 3:17). Someone delivering the word of God speaks by the authority of Christ. He also teaches with the same authority. Going back to 1 Tim 2:12, we see that Paul did not allow this.
I've tried very hard to keep my opinion out of this, since it doesn't matter. I've also tried to present what the Bible says on the subject. I may have missed a point here or there that another might point out. I hope this is helpful.