That is the older style A/C and my manual says the same thing. I haven't seen one of those, so can't comment.
Measure the deflection in the middle of the belt, you're looking for a half an inch and an inch.
The power steering is adjusted by that bolt, loosen the three bolts holding it on and then turn the bolt.
I wouldn't remove the glow plugs unless you're going to change them out, as mentioned, use a 27mm or 1 1/16 inch socket on the crank.

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83 SD

84 CD