2001 Hyundai Accent Check Engine Codes

Engine Performance problem
2001 Hyundai Accent 4 cyl Automatic 53,265 miles

The check engine light came on in my 2001 Accent and then went off. Last night it came on and stayed on, but started flashing. Since last night, it has come on a couple of times, every time flashing. Whenever it flashes, the car starts running rough, like it's not getting enough gas or something. My friend has a code checker (not sure what it's called) and the following codes came on: P0203, P0442, P0300, P0303 and P0301. Is this something I can fix myself? If not, how much should it cost to repair at a shop? I am a single parent and am watching all of my pennies but I need to have my car fixed correctly.