The valve clearances (tappet) are vital to ensure good running of the engine, so is the timing of the pump, it is set by using a dial guage to measure pump plunger lift at TDC of cyl 1 - These procedures are done on every timing belt change. Infact the correct timing belt change repair list for 100,000 kms goes like this.
new timing belt
new timing belt rollers
new timing belt cover foam seal + mileage sticker
new water pump
new camshaft and crankshaft front oil seal
new valve seals
new engine top cover gasket
check and adjust valve clearances
check and time injection pump
check fuel nozzle spray pattern and break pressure.
All of this can be done in the same time they did the timing belt as the water pump is the holder of the injection pump too in a 2C diesel. The camshaft can be removed in another 10 minutes to replace shims to adjust valve clearances and also replace valve seals under them, the valve depress crane tool is used here.
Once everything is bolted back into place the belt is installed and the pump timed. The nozzles are checked and adjusted, the injection pump is primed and the engine started.
Doing this job half way is a sure cause for a headache.