Give the new sysadmin full administrative access to everything he/she will need to do the job. By all means, make sure you retain administrative passwords and keys, but only use them if the unthinkable happens (your sysadmin gets hit by a bus or you have to fire him/her). As other posters have said: expect mistakes, expect the new sysadmin to be less than perfect, steel yourself to accept 'good enough'. Listen. Don't let the shit flow downhill; your job as a manager is to give your staff (even a staff of 1) room to do their job, and shelter them from the sturm und drang in the board room.

What they really need is a genetic modification that leaves the male mosquitos essentially unaltered, but causes the females to have a shortened lifespan, ideally unable to reach sexual maturity. GM males would continue to compete with normal males for surviving females; each successful mating by a GM male would produce a new generation of GM males to continue the process, but all females of that generation would die before ever having a chance to bite a human or breed.

First, there are still many boatloads of legacy Sun equipment out there with proprietary drivers for hardware that's poorly documented, if at all. Access to Sun's source is a leg-up for anyone who wants to understand how such hardware works.

Solaris still has the most scalable SMP tech. There's a lot to be learned by groveling through that code.

Now think about people who have to support large Solaris networks - bugs and all. When you run up against a problem and can't get Sun to admit that it is a problem, your only recourse is to fix it yourself. Try that without source.