I have been asked to do some Excel work, not my best forte really. This will involve writing some vba modules, forms, etc. and some custom menu items. My question is this. Is there a way that if I send the user the custom workbook that when it is first opened it writes the appropriate information to their personal.xls?

Plus hopefully adds/removes my custom menu items to/from their menu bars when the workbook is opened or closed.

You need this..
http://msdn.microsoft.com/en-us/library/aa140936(office.10).aspx

And this...
http://msdn.microsoft.com/en-us/library/aa141014(v=office.10).aspx