Home Audio System questions

It has been eons since I've thought about stereo systems. The left B speaker output stopped working on our vintage Onkyo TX-830 (58 watts) receiver. This brings up questions on whether it's an easy fix, distribute from the A speakers, replace in kind or get up to speed on current technology?

The B speaker outputs fed to an el cheapo 4-speaker distribution box throughout the house via old 'lamp chord wiring'. Are there basic distribution options to send to 3 or 4 speakers as a plug and play solution from the A speakers output?

PM AustinFromSA here on TGR. He owns a high-end A/V company.