I took the conservative approach and order several parts so when I tore it apart, I would have any parts that I felt might be causing the problem as well as a new belt in case the existing one showed signs of wear.
I watched several videos on how to replace rollers and Idler Assembly opting to do the full dis-assembly. The only part that was difficult as removing the front panel assembly. The tabs on the top came off as shown in the video. However, the bottom tabs refused to come off and the video did not mention the bottom tabs. I finally used a straightened out coat hanger that I ran from the side behind the bottom two tabs and grabbed and tightened which popped the tabs loose.
The bearings on the idler assembly were ok, but the plastic wheel was worn and causing the thumping sound and I replaced with no problems and reassembled.
The bearings of the four roller assembly were in good shape as well as the belt, so I did not replace these extra parts at this time.