1996 Stuttering after spark plug change

I just bought a 1996 Neon, it ran fine on the way home from the dealer. I got home and changed the air filter and spark plugs. I went down to fill up with gas and now it does not want to run very well. It seems ok in 1st and 2nd gear but when you go to 3rd and above and give it gas it really stutters and seems like it is not getting gas or something. Also, now the "service engine" light is on. I am sort of wishing I would have left the plugs and filter as they were. I have double checked to make sure everthing is connected and seated correctly. Oh, and I took the instrument cluster out and re-soldered a couple of pins because the speedo quit working on me.......could this have anything to do with the rough running? Please help I need this car to run well.

What codes do you have. That might help you narrow down some of the possibilities.

I am not sure how to determine what the codes are but I believe the check engine light flashed 3 times. I really don't know if that means anything.

What kind of plugs did you use and what gap?

Look at this thread to check the codes...
http://www.automotiveforums.com/vbulletin/showthread.php?t=625404

The plugs were Autolight from Walmart, I went with what the Fram book said. I have since taken them back out and threw them away. I put the old Champions back in and the car is working fine. I was able to figure out the codes, "random cylinder misfire" and "cylinder 4 misfire". Got the "service" light cleared and all is good now.

The stock copper Champion plugs do work best for the neon. Good to hear all is well now.