Rybak, 53, of Independence, at first pleaded not guilty to the five counts against him -- bribery-related conspiracy, theft from labor unions, theft from employee benefit funds and tampering with a witness and conspiracy to tamper with a witness.
Then in October he and his attorney John Corrigan worked out a plea deal where Rybak would plead guilty and testify against others in the probe.
In his plea agreement, Rybak admitted doing favors for Dimora in exchange for the commissioner using his influence to land county jobs for two union members and a raise for Rybak's wife, Linda.
Those "favors" included installing a gas line for a pool heater, attaching plumbing fixtures to an outdoor bathroom and winterizing an ice machine.
Dimora has been charged with 26 counts and is scheduled to go to trial in September. The FBI and IRS went public with their joint Cuayhoga County corruption probe in July 2007. More than 30 people have been charged in the probe to date.