It's really managements problem to ensure you leaving does not impact badly on the company. Your main responsibility is to handover in whatever fashion they want and focus on the big change in life you're about to start.
Your 'special skills' seem to come from experience, this isn't something it's possible to teach I would think. They can always call you in from retirement and pay you to help out if they need to.
As far as plans go, this is what works for me. A handover document is prepared which contains a break down of all duties that go with the role. All passwords and things like that, ip addresses whatever. This is not a transfer of all your knowledge, it's a reference for your successor. It should document all procedures that are relevant and importantly, any workarounds and modifications that you have made up over the years.
Then when the time comes for you to leave, you work with your successor for a few days, using this document as a baseline and modifying it as need be until you actually leave. This pretty much gives them a nice overview of everything and a reference to fall back on. From time to time I've been called to ask clarification on something, but very rarely have they needed me to go back in for anything. So long as the document is thorough it should go smoothly.
It doesn't take long to create this document, I'm assuming you don't have a million different roles. In the past it has taken me a couple of hours, to a day or two at most, with a bit of tweaking as I recall something left out. Possibly I have even spent more time formatting it for prettiness and putting logo's on and suchlike than actually composing the doc.