Like most if not all diesel engines the CRD is an interference engine so when timing goes valves and pistons try to occupy the same space. If all goes well the roller bearings on the rockers collapse as designed and all you have to replace are 16 rockers/lifters at ca. $46 per set (1 rocker/1 lifter), maybe a bit less per Wobbly at
viewtopic.php?f=35&t=65556 plus labor. See my post down toward the bottom of
viewtopic.php?f=5&t=65450&p=721088&hilit=timing+bee#p721088 for some helpful how to links. Don't know where you are but if near another forum member lots of folks are willing to help out and some, like myself, have the tools on hand.
Cost. Minimum DIY $75 for a Gates (T336) from Amazon and about 5-6 hrs of labor, assumes all the spinning things have solid bearings with no slop and not weaping grease. Maximum DIY including just replacing all appropriate spinning things plus the water pump about $600 in parts, depending on how hard you shop, and a decent weekend of work as the water pump adds about 4-5 hours of extra labor. DIY assumes you have the right tools or an effective substitute to pin the cams, flywheel, and lock the cam sprockets in place. Paying to have the complete job done including water pump is reported to run ca. $1,600 but finding a place qualified and willing to do it can be a challenge.
Cost of not doing it take a look at
viewtopic.php?f=5&t=64557 and
viewtopic.php?f=5&t=65084