plug wire problems

I took my 99 Jimmy to the dealer for a tune up 2 months ago. At that time the changed the plugs(there was no way I was gonna touch that)and I told them I'd change the wires. Easy job right? Well I replaced the wires 1 at a time just like dad showed me 20 years ago in order to keep the firing order intact. I started my vehicle and it is running rough. Lthe whole thing shakes like I put a crane cam in it! Also, the service engine light came on. I shut her down and double checked all the wires and they all seem to be on there pretty snug. Fired it bach up and it is stii rough and the light is still on. Have any of you ever had this problem or heard of it? Thanks, Jp

check and make sure none of the wires are touching each other. When I changed mine one time i had some of them touching and it would misfire.