Okay, I'll write a tutorial, but here's a quick overview:
Every saber must have a .sab file. Look in our pk3 files (with WinZip) and you'll see all of ours in ext_data/sabers.
There's a lot of fields and it can be confusing, but look at one of our .sab files for an example.
Now, you'll notice that you specify the model of the saber in that .sab file. You'll find all our models in models/weapons/... (whatver the actual saber directory is).
You can view our saber models with ModView, which I think James already released. The important things to have in the model are:
1) proper scale - so it's not too big or too small
2) proper orientation - so that it sits in the hand correctly
3) proper tags - there is a tag named "*blade#" (where the number is 1-8) for each blade. If you have one blade, you just need a *blade1. If you have two, you need a *blade1 and a *blade2. If you have six, well... you get the idea.
If you plan on making your own saber hilts (or modding ours), I recommend MilkShape (which has a GLM importer you can download) as it's very easy to use (even I have made new weapon models with it and I'm just a programmer!)
Once all this is done, you should automatically be able to use it in MP (it'll appear in the menu). In SP, it won't automatically appear in the menu, but you can modify the list of sabers in the .menu file for the saber menu. But you can also just use the "saber" console command.
Like I said, I'll be writing an actual tutorial on all of this, but, for now, this should get you modders a good start!