Hi Owen
Just to add my tuppenceworth. A good place to start is here:
http://www.apple.com/training/
I can see what some of the other guys are saying, but does that make all education worthless? OSX Server 10.4 Essentials Course is 4 solid days. You really must have an understanding of CIDR, Networks, physical structure as well as what can be done in GUI, a good knowledge of 10.4 client before you even consider taking the course, otherwise its money wasted.
There is a lot of literature out there that is outstanding, but unless you know the basics, most of it is going to go over your head. As with all things, good education and practical knowledge are invaluable. One thing I will say that is crucial – and this is where most guys stumble on – is DNS. An understanding of what this is and how it works is an absolute requirement if you want to play with some of the more advanced technologies built into OSX Server, or any other server for that matter.
HTH