I would react the same way if a born-again believer did not preach on these.

The Bible clearly teaches about Hell and repentance. If it's not important, why is it in the Bible? Because it is important. 

 About repentance:

"The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to usward, not willing that any should perish, but that all should come to repentance." 2 Peter 3:9 

"And the times of this ignorance God winked at; but now commandeth all men every where to repent:" Acts 17:30

"Likewise, I say unto you, there is joy in the presence of the angels of God over one sinner that repenteth." Luke 15:10 

"And saying, Repent ye: for the kingdom of heaven is at hand." Matthew 3:2

About Hell:

"And if thy hand offend thee, cut it off: it is better for thee to enter into life maimed, than having two hands to go into hell, into the fire that never shall be quenched:

Where their worm dieth not, and the fire is not quenched." Mark 9:43-44

"The sinners in Zi'-on are afraid; fearfulness hath surprised the hypocrites. Who among us shall dwell with the devouring fire? who among us shall dwell with everlasting burnings?" Isaiah 33:14