99 Grand Marquis turns but wont start

I have a 1999 Mercury Grand Marquis. I had  the check engine light on so I had the
codes read and it said misfire on cylinder 1 & 6 check spark plugs. Changed the spark
plugs, seemed like everything was fixed it was running much better. Couple days
passed and the code did not go off. Had the codes checked again just to make sure it
wasn't something new. Got the same code. I needed to clear the code to go pass
emissions test for dmv registration. Someone at the auto parts store recomemeded
resetting the computer by disconnecting the battery and letting it set for 30min-hour
and then reconnecting the battery. I did this but now that I've reconnected the battery
the car won't start. The engine turns but does not start. Tested the battery it's good.
Check the fuses, they're good. I put a couple gallons of gas in just in case the fuel
gauge was off. I can here the humming of the fuel pump with the key in. Is there
anything else I can try before I take it to the mechanic?