You can do it without removing the head, the tappets are under your camshafts so you need to remove em both before you can do the tappets.
Take out spark plug #1 and turn the engine over by hand with a spanner on the camshaft sproket until you get to TDC # Piston 1. I found I got even resistance turning it, then it would 'jump' to TDC & piston 1. Double check by shining a torch down the hole or putting something soft like a dowl rod down it so you can see the piston reach the top of its travel.
Then put loads of tipex marks on all the sprokets & timing belt so you can put it back on the same way it came off, remove the valve cover and note the position of the cams, & mark the sprokets & chain. Then take out the camshafts, you need the Haynes for this as you need to loosen them progressively, PM me and I'll send u a PDF version
Then its a case of puting the cams back in, line em up & transfer the marks from the old chain to the new one. Nothing else should have moved, but you still have the timing belt marks you can use to check
