Vintage Motobécane – ID help & advice for fixing skipping chain

Hi everyone,
I brought home this beautiful vintage Motobécane from a trip. It has a classic frame-mounted shifter and rides great, but when I pedal hard the chain skips violently on one of the cogs.

Could anyone help me:

1. Identify the exact model/year from the attached photo.

2. Figure out which parts I should replace to fix the skipping (chain, freewheel, chainrings, etc.). And also, where to get such parts.

Thanks in advance for any tips!