There is no chain on a CRD they are belt drive.
If you are in Europe SKF do a nice full kit of quality parts, don't be tempted to skimp and use cheap Chinese parts. Replace the water pump, idler and tensioner, insurance against expensive failure.
You will also need to replace the coolant - use only HOAT.
While you are doing this it is worth checking the Serpentine Belt....this drives the Alternator etc.
Check the Alternator Pulley at the same time.
Also change the Idler Pullies which the Serpentine belt runs on....some of the Pullies are held on by Left-hand thread bolts! If the Serpentine belt is not running neatly on the Pulleys you may need to replace the Belt Tensioner and its pulley!......been there done that!