Resetting the tensioner can be tricky. It is best to put it in a strong transparent bag as soon as you take it out. Reset it just before you reinsert it by reassembling it inside the bag. This prevents that part fly all over your workshop (don’t ask how I know). The tensioner should be assembled so that the inner part stays in, this may be easier said than done.

It is not necessary to split the timing chain, if you remove the rocker arms and the rear camshaft covers you can side the cams backwards. You will need some kind of valve depressor to remove the rocker arms. When reassembling make sure that the chain wheel bolds are properly torqued (100Mn, almost as much as the headbolds).

I would strongly advise to start now spraying penetrating oil on the exhaust bolds.