Warren Buffett is the former CEO and chairman of Berkshire Hathaway. Johannes EISELE / AFP via Getty Images Warren Buffett's cash pile is a boon, Tom Russo said ahead of Berkshire Hathaway's annual meeting. The veteran investor shed light on how Buffett managed the firm from his Omaha office. Greg Abel should take care not to harm Berkshire's reputation as a trusted acquirer, Russo said. Warren Buffett's cash hoard is a blessing, not a curse, and Greg Abel must be careful with his more hands-on approach, veteran investor Tom Russo told Business Insider ahead of Berkshire Hathaway's annual shareholder meeting. Abel succeeded Buffett as Berkshire Hathaway's CEO at the start of this year, taking charge of the conglomerate's $373 billion of liquid assets as of December 31. That reserve has ballooned in recent years as Buffett, perhaps the world's foremost bargain hunter, has struggled to find stocks and businesses worth buying.…