Cylinder Misfire codes thrown

[Snow Boy]

1998 S70, recently did complete tune up and was running fine for a few weeks after. car starting stumbling so, ran for diag codes and found that P0302, 03, 04, 05, and 07 came up. I recently had the Serpentine belt changed and the mechanic replaced the plastic wires around the wires going to the spark plugs. But it wasn't quite running right even before he did the work. Any recommendations. Also through a P0410 code, any remedy's? Thanks