Our configuration manager is leaving for a new job and now the office is crumbling.

How do you deal with person dependencies at your workplace?

This is a critical subject. I strongly believe there should be succession plans for all critical employees. There should also be cross-training in the event a critical employee is not available such as the case you are describing.

Finally, there should be detailed documentation that another employee can pick up and continue the process.

In the case that you are describing would any or all of the above have helped?

There has been some training and he's trying to document everything. He even held a meeting where we could ask questions and he showed us the most important stuff, but I don't think it will matter in 6 months when something needs fixing.

Document the shit out of everything. I try to comment nearly as much as I write actual code in the hopes that anyone can read through the source and understand the logic and what my approach was. Also, cross train like crazy. There's never a legitimate reason why any mission critical operations should only fall under the purview of an individual.

Usually with a thick rope and some duct tape.