To replace the imaging unit in your Lexmark printer, follow these detailed steps. Begin by turning off the printer and allowing it to cool. Open the printer cover and locate the imaging unit. Press the release tabs or buttons and carefully remove the old unit. Unbox the new imaging unit, and gently shake it to distribute the toner evenly. Insert the new unit into the printer, making sure it clicks securely in place. Close the printer cover, power on the device, and wait for the initialization process to complete.