Engine light on dahboard

I havnt owned a car that has had these warning lights, but after reading some threads; in order to find the problem I need to buy a reader that plugs into a socket by the centre console, and it will tell me what fault to fix.

So will I will buy a reader from ebay, to read the codes, and sort the problem. Is that a good plan. I fixed cars 25 years ago, but I am a little rusty with modern engines.

I have just bought a 2003 scenic 1.4