what does my car suppose to idle at when it is in gear.

What is your question?

I had a tune up,with someone i have used before.plugs wires,etc.also transmission was flushed and added new fluid,then had the cv joints changed.when i picked it up it was idleing real low,and the engine sounds like a log truck.and they say there is nothing wrong,but i had to argue with them.that it was running fine when i brought it in.i also am aware that when a battery is unhook,the car has to rethink.so after a week it sometimes idles low about 500 rpms.when you stop.and still there is a faint miss,even after they said they tuned it up.we paid 900 dollars for all the repairs.and it is running crappy,and they there is nothing wrong, and being mechanically inclined i cant figure out what is wrong,can you help?