Oil filter ISTR is just under the induction air pipes, to the right hand side of the engine as you lift the bonnet, you have to remove the air ducting which being French is extremely brittle and prone to breaking, best done on a warm day or in a warm garage.

Fuel filter is behind the oil filter, it should have a heater which you can remove from your old filter and refit to the new, seems a bit fiddly but it does work, do not be conned into paying over £70 for a filter with a heater already attached, even without the filter is not cheap, i think it was around £35 for a good make pattern part from a factor.

This was the situation on our 1.6D Citroen, Pug version should be similar.

Its not partcularly hard to do but if its your first time with a Diesel this is not the easiest filter change to learn with, suggest you enlist the help of someone who's worked on Diesels before to help you.

Most important to check the primer works properly before removing the old filter, will be extremely difficult to prime the new filter if that bellows has failed, its across the back of the engine.

20 quid on a Haynes manual would be money well spent.