Reading through the indictment shows that Manafort and Davis are, in general, charged with crimes arising from their effort to conceal income earned in the Ukraine from US tax laws and deny their lobbying in the US and abroad for the Ukrainian regime of Victor Yanukovich. As Ukrainian president, he came to be viewed, not only as financially corrupt, but as the Kremlin's man in Kiev. He was forced to flee to Moscow in an uprising by pro-European anti-corruption Ukrainians. There is no reference of Manafort's connection to Russian oligarchs or any direct involvement with Russian entities.
Trump has no need to be concerned about anything explicitly stated in the indictment. All criminal charges are entirely extraneous to the 2016 campaign. If Manafort has any dirt on Trump he may bargain for a better deal, but that is beyond our ability to know.
Note on jonas comment:
Trump's open collusion with the Russian hacking scheme by constantly referencing Wikileaks revelations during his campaign and exhortation for Russians to hack Clinton's server to find unpublished emails are not criminal offenses in and of themselves. Trump engaged in collusion without necessarily being involved directly with Russian agents. For good or ill, "collusion" is not a specific federal crime. The media have confused the issue by using the term as if it were an indictable offense.