L_U_K_E_191

i have been told that my cylinder head needs replacing on my focus 1.8 TDDI i didnt know if i could fit a cylinder head from a TDCI or if it has to be a TDDI cylinder head any help or advice would be appreciated.  

i have recentley replaced the head gasket on my focus 1.8 tddi i sent the head off to be skimmed and for the valve stem seals to be replaced. put the car back together and it started and runs fine but once you put the car in gear and drive it you can hear a knocking/tapping noise coming from the engine i have had a few people listen to the noise and have been told by all off them that its the tappets. i have been told that they need to primed before running the engine is this true??? and how can i do this the car itslef runs fine and no loss of power or misfire its just the noise that dosent sounds healthy

any ideas??

thanks