To change guide rail and tensioner, remove the inlet manifold and cam cover, remove ignition coil pack/distributor,remove upper chain tensioner, remove upper chain cover, unbolt one of the cam sprockets, remove the upper chain and tie it up, remove upper guide rail, replace tensioner for new when reassembling.
If re-using old tensioner, it will need bleeding, do this by inserting wire into end of piston till it collapses.