Check engine light on, misfire on cylinder number three

I was driving home one night and noticed a loss of power, no check engine light. I woke up the next morning to drive it and noticed the check engine light was on. I took it up to an AutoZone to use a scanner and it came back as a "Misfire In Cylinder number 3". There was no knocking, rough idle, no white smoke or smoke at all, just a loss of power. I assumed it was either the spark plugs or the Ignition coil, so I replaced the ignition coil on cylinder 3 and put it all new spark plugs. I noticed the new spark plugs were a tad shorter in thread length, and I found out after putting them in that they were gapped at.036 and not the factory standard of.035. After putting in new plugs and the new coil, there is now a rough idle, a weird sour smell, loss of power at low RPM and the check engine light is still on. I'm wondering if I need to find better spark plugs that are a closer match to the ones that came out, or maybe put the old ones back in as they only had about 30,000 miles on them and are slightly discolored. Thanks for any and all advice.