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.