Renault Traffic 1.9 Diesel

1) I would like to know if you can regulate the valves of my traffic ... since the mechanic put a totally new cylidos lid ... and says that the valves can only be regulated before assembling and closing the engine ... the problem is that I stay with a
lot It only starts hot whether the calynech twice for 5-6 seconds .. the heating spark plugs are new original bosch and starts as bad as before ..