Hoover hnmf2605a fridge freezer

I have a hoover model hnmf2605a, the fridge has started to freeze the food inside,I have run it on temperature setting 3 then gradually turn it down to 1 but the compressor still runs continually, after reading the forums I think as a start I will relace the thermistor which I have ordered, I need to know how to access it , I know it is “foamed” in but what do I have to strip down to gain acces to replace,, the drain off hole and pipe is clear of any blockages,,, many thanks,,,