Peter and Paul's different gospels?

Mark 1:14  Now after that John was put in prison, Jesus came into Galilee, preaching the gospel of the kingdom of God,

Mark 1:15  And saying, The time is fulfilled, and the kingdom of God is at hand: repent ye, and believe the gospel.

Mark 9:31  For he taught his disciples, and said unto them, The Son of man is delivered into the hands of men, and they shall kill him; and after that he is killed, he shall rise the third day.
Mark 9:32  But they understood not that saying, and were afraid to ask him.

Also, In Lk 18:31-34 the 12 knew nothing about Christ' death, burial and resurrection. (DBR).  But they already had been preaching "the gospel".  Which one?  The gospel of the kingdom.

Luke 18:31  Then he took unto him the twelve, and said unto them, Behold, we go up to Jerusalem, and all things that are written by the prophets concerning the Son of man shall be accomplished.
Luke 18:32  For he shall be delivered unto the Gentiles, and shall be mocked, and spitefully entreated, and spitted on:
Luke 18:33  And they shall scourge him, and put him to death: and the third day he shall rise again.
Luke 18:34  And they understood none of these things: and this saying was hid from them, neither knew they the things which were spoken.

John 20:8  Then went in also that other disciple, which came first to the sepulchre, and he saw, and believed.
John 20:9  For as yet they knew not the scripture, that he must rise again from the dead.

They didn't believe He rose.  They believe His body was stolen as was told to them  by the women.  

John 20:2 KJV   Then she runneth, and cometh to Simon Peter, and to the other disciple, whom Jesus loved, and saith unto them, They have taken away the Lord out of the sepulchre, and we know not where they have laid him.

Paul’s gospel content:

1Cor 15:1  Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;

1Cor 15:2  By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.

1Cor 15:3  For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;

1Cor 15:4  And that he was buried, and that he rose again the third day according to the scriptures:

From these verses we find that the 12 were preaching a "gospel" while Jesus was still alive thus it did not include Christ' death, burial and resurrection.  We also see that when Jesus explained His death and resurrection, they didn't even understand it.  And this was years of walking with Christ.  Again proving they did not know or have clue of the gospel that Paul preached.  Because Paul's gospel is where we get saved today.  It is to believe that Jesus Christ died, shed His blood, was buried and rose from the dead for the forgiveness of our sins.  And once we believe and put our trust in that work on the cross we are saved for eternity.  

Did Peter and Paul preach the same gospel?  Impossible.  Do you remember "doubting Thomas"?  What did he doubt?  That Jesus rose from the dead.  Was Thomas preaching the gospel that included the DBR of Christ as it was a requirement for salvation in Paul's gospel?  Impossible.