BE CAREFUL! This is not an area where you can afford to make a mistake. You question leads me to believe that you do not have alot of experience with chains/tensioners etc. While I understand folks wanting to do some of their own work, you have to realize that if you make a mistake with this project, the consequences can be a bunch of bent valves.
The guides in the heads are held in place by threaded roll pins. There is a special tool for removing these, but you can make your own with a (6x1.25-I think)long bolt,nut and a short sleeve or tube, to fit around the pin as it slowly works it's way out of the head. Of course to access the pins you need to remove the alt & ps brackets.
You do not "adjust" the tensioner on one of these v-8's. My suggestion is if you are replacing a chain with over 100k on it, just buy a new tensioner too and install it.
Do your work ie: changing the chain & upper rails, with the tensioner removed. Use a 27mm socket to turn the engine over BY HAND and doulble check ALL timing marks before starting the car when you are done.