why does my van idle a little rough while in gear stopped at a sign/red light?

What is your question?

when I start it up, all is fine. driving, all is fine. when I stop at a red light or stop sign, it idles a bit rough. when I put it in park and idle, all is fine. It is only when it is in gear and idling. I have been told that it could be the coil, plugs, wires, motor mount, or possibly something inside the motor. I have been told that I should start with the coils, the most expensive parts. and if I were to do so, should I have them all 3 done at once or can they be done one at a time? also, do I need to have the plugs and wires replaced at the same time or can all of these be done a week or so between each other?