The gospel of Jesus Christ: What is it?

[Arkady]

Are there telltale signs I should be looking for?

There are. Apart from the ones you've mentioned:
-if he properly realizes the fact that this present world is literally going to hell <!-- s --><img src="{SMILIES_PATH}/smile.gif" alt="" title="Smile" /><!-- s -->
-if he doesn't turn aside from the teaching and doctrines of the Church (Christ's, apostles', bishops', fathers',..)

examine his works if he has any:
-if he's defended the Orthodox faith against the unholy and impious
-if he's written anything on theology
-if he's written anything on prayer and penitence
-if he's written anything in which he interpretes the Holy Scriptures or\and the writtings of the Church fathers
-if he's written/preached any sermons/homilies
-if he's composed any prayers (that work)

Arkady. Russia.