There is nothing simple about replacing the wires. They are a pain unless you have small hands. I am not saying it can't be done but you need to do some disassembly to get at them. How many miles on the vehicle? The closer to a plug or belt change make it easier to take the engine down. I replaced all the wires at the same time I did the TB, WP, Idler Bearings, Plugs and Valve Cover Gaskets. I removed the cowl and windshield wiper motor assembly when I did it. I also replaced all the hoses on the backside of the engine. The Y-Pipe and hose will go bad and leave you stranded or worse an overheated engine. When you replace the wires they need to go back in the same order they were in. If not you can get a cross fire effect. The KiaTech site has some diagrams that help. Take pictures and refer back to them as needed.
Did the recall on the ICV get done? A screw coming loose could cause the miss also.