I will assume your question is sincere.
You need to do exactly the three things I pointed out priest or not.
1) you must know and acknowledge his sins in detail by a detailed examination-of-conscience,
2) you must have a ‘firm-purpose-of-amendment’ agreeing to sin no more as much is humanly possible, and
3) you must make an ‘act-of-contrition’ similar to this prayer:
“On my God, I am heartily sorry for having offended Thee, because I dread the loss of heaven and the pains of hell, but most of all because I have offended Thee , oh my God, who are all Good and deserving of all my love. I firmly resolve with the help of they Grace to confess my sins, to do penance and to amend my life. Amen”
IF the person is properly disposed to properly perform the three steps above and makes what is called “A Perfect Act of Contrition” by essentially forgetting about ‘the loss of heaven and the pains of hell’ but purely because their sins have Offended the Father, then they may have their sins forgiven by God - we don’t know because we are not Him.
BTW, I have had this discussion with very faithful protestants who have agreed that these steps would likely save a sincere sinner.
again if you are sincerely interested you could read this link and should understand the position of the Church essentially unchanged since the Didache from the first century.
http://www.newadvent.org/cathen/11618c.htm
the Didache: http://www.newadvent.org/fathers/0714.htm
AMDG
So what happens in my question? Forgiven? Heaven or Hell if you don't make it in time to the priest? We'll have to see what keeps someone OUT of Heaven, if they were bound there in the first place...
Exodus 32:32-33
But now, if you will forgive their sin—but if not, please blot me out of your book that you have written.” But the Lord said to Moses, “Whoever has sinned against me, I will blot out of my book.
Daniel 12:1
“At that time shall arise Michael, the great prince who has charge of your people. And there shall be a time of trouble, such as never has been since there was a nation till that time. But at that time your people shall be delivered, everyone whose name shall be found written in the book.
Philippians 4:3
And I intreat thee also, true yokefellow, help those women which laboured with me in the gospel, with Clement also, and with other my fellowlabourers, whose names are in the book of life.
Revelation 3:5
He that overcometh, the same shall be clothed in white raiment; and I will not blot out his name out of the book of life, but I will confess his name before my Father, and before his angels.
Revelation 13:8
And all that dwell upon the earth shall worship him, whose names are not written in the book of life of the Lamb slain from the foundation of the world.
Revelation 17:8
The beast that thou sawest was, and is not; and shall ascend out of the bottomless pit, and go into perdition: and they that dwell on the earth shall wonder, whose names were not written in the book of life from the foundation of the world, when they behold the beast that was, and is not, and yet is.
Revelation 20:11-15
"Then I saw a great White Throne and him who was seated on it. Earth and sky fled from his presence, and there was no place for them. And I saw the dead, great and small, standing before the throne, and THE BOOKS WERE OPENED. Another book was opened WHICH IS THE BOOK OF LIFE. The dead were judged according to their works as recorded in the books. The sea gave up the dead that were in it, and death and Hades gave up the dead that were in them, and each person was judged according to their works. Then death and Hades were thrown into the Lake of Fire. The Lake of Fire is the second death. If anyone's name was not found written IN THE BOOK OF LIFE, he was thrown into the lake of fire."
Revelation 21:27
Nothing impure will ever enter it, nor will anyone who does what is shameful or deceitful, but only those whose names are written in the Lamb’s book of life.