Zanussi ZBB7266 intergrated fridge freezer warm fridge but freezer works

[honey33]

my zanussi fridge freezer momber stated above has all of a sudden gone worng the fridge part is warm even though the digital display shows +5 and the freezer is working just fine and splay is correct also on -18. now i had someone come to look and talk about a quick look didnt even check anything but said it is NOT the thermostat and the vents are clear and doesnt seem to be any build up ice and fan i think also seems to be working..the digital display inside frdge seems to work but cant be giving the correct temp of fridge as says +5 and it is no way near that at all more li +18...so my question is the man that came says its the circuit board which i assume means the one to the thermostat and says it will cost that much to replace you better off with new appliance.but this cost m799 pound 1 and half year ago....so please does anyone know about fridge freezers and do you think the man is correct in what he says or is it worth me trying to do anything to fix it myself or get anyone else...many thanks