I have a 201 hyundai tiburon with 148000KM. It's a 2.0L DOHC everything has been going fine with it until recently I didn't start it for a week.. and when I tried to it had a really rough time starting.. and when it did finally start, it was running really rough, but eventually smoothed itself out when running at idle. But while idling it has a small sputter from time to time, almost like something is skipping a beat, or not firing when it should. My question is should I go out and replace the spark plugs and ignition wires or could it be something more serious?

How old is the gasoline in the tank? Sometimes when my Jeep sits for a few days the start up is rough and until the engine is warmed up enough it runs rough. Try putting in high test and see if that helps. Or run the engine for at least 1/2 hour or more at speeds over 50 MPH. In the winter my Jeep does this a lot until properly warmed up and then it's just fine.

. Replace the platinum spark plugs with the exact ones that came in your Hyundai, if they have more than 45,000 km on them.

. Replace the fuel filter.

Spark plugs have only about 10,000 on them. The car will still seem to "skip a beat" at idle even after its been running for hours. I only run high test gas in this car.

Try cleaning the Idle Air Control Valve, throttle plate, upper and lower ports, and throttle body. Afterwards, wipe the air box out with a damp cloth, allow it to dry, and change the air filter if it has more than 40,000 km on it.

Even though this link is geared to Hondas, the gist of it is applicable to many vehicles:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-7.html#post1054149

You mentioned that you replaced the spark plugs already; have you also replaced the plug wires?

You can also try adding a bottle of water remover to your gas tank. My car just did the same thing after I let it sit for the weekend.