There are a couple of timing chain replacement faq's out there, and it's not too hard, as long as you take your time, and have 3-4 hands!

The guide replacement has been documented as well.
The guides aren't all that bad either, but they do require removing the power steering pump and bracket on the drivers side, and the alternator and bracket on the passenger side, just to get to the front of the heads.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...