[Corpsecorps]

I've been having a look at the NetInfo Manager and it seems quite obvious that it shouldn't be too hard to use that in conjunction with a few other tweaks to give a user a new name.

Seems equally apparent that i could really screw the system if i don't know what i'm doing.

Also, i'd like to know how to create a "Group", so i can make certain accounts able to access certain directories, but not others.

[slugslugslug]

Go here and click on ChangeShortName in the left-side navigation area. There's a tool to let you do it (it comes with lots of warnings about the risk involved)..

I can't help you with the groups, but I'd bet there's an OS X book out there that could, if you feel like heading to your local store and flipping through the pages..

[Corpsecorps]

Thanks for the link.

I'd like to know how to do it, but as i'm in a hurry this is better.

[Angus_D]

If you really care about the specifics:

Mac OS X: How to change user short name or home directory name

You can also create groups in NetInfo Manager. Look at the existing ones to see what attributes you need.