Q: Car idles rough when stopped at light or stop sign (not all the time). Car overheated very briefly.

2001 nissan altima overheated briefly last week (as soon as temp went high, check engine light came on for coolant ), vehicle was stopped. Radiator was checked and it was pretty empty. After radiator cooled down water was added and temperature gauge stayed normal. Radiator rusty so radiator flush done. Coolant still seems to have a small leak but not sure where. Due to high mileage and not sure when spark plugs/distributor cap/rotor and wires were changed those are being done this week. Check engine light just came on it was P303 for cylinder 3 misfire. Now with doing some research online it looks like the Nissan Altimas are known to need to have intact manifold gaskets replaced. How can you tell if it is the intact manifold gasket ? Also they say it is best to change both gaskets, is that true ? The car is not giving off any white smoke and the engine temperature is staying right in the middle range, it hasn't overheated again.

My car has 205000 miles.
My car has an automatic transmission.