Top of fridge warm, bottom freezing

I've got a 6 year old fridge freezer and for the past few weeks it has become warmish near the top of fridge compartment.
The freezer compartment is still working perfectly, and the bottom of the fridge is still very cold (and things stored in the crisper might even freeze).

There are two vents within the fridge compartment for circulating cold air, one near the top which has stopped working and there's no cold air at all coming out of it, and one in the middle which is still working, but the air doesn't seems too cold but I didn't actually notice what it used to be like previously.

Does this sound like something I might potentially be able to fix myself? If not myself could be it fixed by an engineer, or might the whole thing need replacing?

 

A model number may be helpful.

 

I would check to see if the coil has iced up. It's usually in the back of the freezer compartment. Freezing can block the airflow passage down to the fridge so the cold air is trapped in the freezer and can't get down to the fridge.