Fan problem

[tommy99]

The fan on my cooker hood has virtually ground to a halt though it is still spinning slowly. I suspect the bearings may be clogged with grease (but don't know for sure).

I have tried to open the fan casing so I can clean it but I can only get to 3 of the screws without taking the whole cooker hood off the wall. There is at least 1 screw that I can't get to and if I could I can't be sure I will be able to get into the casing.

Has anybody done this before/got any instructions?
Any tips would be much appreciated.

The cooker hood is a Hygena APP2540.

Thanks