02 Saturn l200 WON'T start. Mechanic changed coil pack,and plugs,no bueno! Why?

What is your question?

Got an oil change at local Wal-Mart. Later same evening, wouldn't accelerate properly. Parked it,to keep from causing any further possible damage. Car wouldn't start next morning.Check engine light was on. Read coil pack missfire. Had mechanic replace worn plugs and coil pack. Mechanic still trouble shooting after STILL not starting.Replaced timing chain 6 months ago. Seems fine. Serpentine belt not completely worn yet. Car is at 198,000,so I guess she's ready for retirement! (Didn't have this problem prior to my visit to Wal-Mart,but I'm certain that this has nothing to do with the service I received.)