A: Actually the statement that Jesus descended into hell is a product of the Apostles' Creed—an early extra-biblical statement of Christian belief that is still used by believers as a kind of statement of faith. The Apostles' Creed goes like this:
I believe in God the Father, Almighty, Maker of heaven and earth: And in Jesus Christ, his only begotten Son, our Lord: Who was conceived by the Holy Ghost, born of the Virgin Mary: Suffered under Pontius Pilate; was crucified, dead and buried: He descended into hell: The third day he rose again from the dead: He ascended into heaven, and sits at the right hand of God the Father Almighty: From thence he shall come to judge the quick and the dead: I believe in the Holy Ghost: I believe in the holy catholic church: the communion of saints: The forgiveness of sins: The resurrection of the body: And the life everlasting. Amen.
When the Apostles' Creed took its English form sometime in the sixteenth century the Greek word hades was translated "hell" even though the typical biblical word for hell was gehenna.
In Acts 2, when Peter quoted David speaking prophetically concerning the Messiah he said: For you will not abandon my soul to Hades... (Acts 2:27 ESV) The word hades simply refers to the abode of departed spirits which is why the NIV translates it grave. That is also why several English translations of the Apostles' Creed have changed that line to say: ...he descended to the dead.
So, in answer to you question, no, there is really nothing compelling in the Greek of the New Testament that would reveal that Christ descended into hell. In fact, if we cite Jesus' own words, we will remember He promised the penitent thief that "...today, you shall be with me in Paradise." (Luke 23:43) Personally I'm more comfortable sticking with the Lord's own words to explain where He went after His crucifixion rather than on some creed.
Some might argue that Ephesians 4:9 supports the Apostles' Creed since it speaks of Jesus descending into the lower earthly regions. They assume this phrase refers to hell, but once again it could just as easily refer to the grave.
That brings me to your second question: Is there danger in teaching that Jesus descended into hell?
I believe there is. To believe such a thing certainly begs the question of why Jesus would need to descend into a place of torment and suffering. Some have sought to answer that question with the idea that Jesus spent time in hell suffering torment on our behalf. But that would be completely inconsistent with our Lord's victorious cry from the cross when He declared "It is finished!" (John 19:30) just before dismissing His Spirit. That phrase essentially means, paid in full. So to say that our Lord's suffering on the cross was somehow incomplete or needs to be ongoing is to open up a theological can of worms. Frankly, it's not far from the unbiblical idea of the Roman Catholic Mass, where Jesus is believed to sacrifice Himself over and over at each Mass.*
I have no doubt that the Apostles' Creed was worded in such a way as to make it very clear that Jesus died in a genuine and literal manner. It was not meant to suggest or teach that the suffering of our Lord was extended beyond the cross, or that what He accomplished there was insufficient or incomplete.
* Quote from Catholic Education (catholiceducation.org): "The Holy Mass is the holiest thing we have here on earth. Why? Because it is the action of Christ. And what does Christ do in the Holy Mass? He offers himself for us, as he offered himself on the Cross. He sacrifices himself for us. That is why we say that the Mass is the same Sacrifice as that of the Cross renewed in an unbloody manner on the altar."