tapping noise from engine.

[cargo]

You valve clearances could be out of spec without making any noise.
I'd do them anyway if they've not been looked at for a while
Intially all you need to do is measure the clearances no cost except in time and effort.

Replacing the camchain is not too difficult see the other thread on this.
One thing to be carefull of is refitting the tensioner it is a ratchet mechanism and if you get it wrong the camchain could be over tensioned.....................NOT GOOD