an FSM (factory service manual) would clear up those questions very quickly. try finding one for download online somewhere. should be more than a few copies floating around.
to replace the tensioner and remove the second guide you will have to remove the valve cover, the distributor and the front upper timing cover.
archive thread with a DIY:
http://zilvia.net/f/showthread.php?t...t=timing+chain
make sure the follow the step marking the distributor very carefully or else you will have to retime the motor.
this is the front cover:
http://www.autozone.com/images/cds/j...3d8017f246.jpg
this is an exploded view of the components:
i've circled the upper chain guide, the "lower" chain guide, and the tensioner in red.
RTV silicone is supposed to be applied to the half circles of the valve cover gasket.
if you're still confused there are plenty of write ups on the net that are more detailed. just do a search on google for "ka24de timing chain guide diy", or something to that effect.