Hi Leigh, thank you for your question. I found myself in a similar situation a couple of years ago when I designed an interface for a multi-user Access database. I had to not only design how the system could be used by more than one person, and actually sell the database to each individual in the company. I'm not sure if I was successful or not but at any rate to answer your question, I have found, in more recent years, examples of documentation that may suit you for this project.
There is a difference between taking a user by the hand, and, in step-by-step instructions, illustrate for them how they are to use the program. This is your basic User Guide. In it, an author would specify the different elements of the program; e.g., Forms and Tables and Queries and how they relate. You would explain that all information is stored in Tables in a database, and each time they run a Query, it takes space on the hard drive to save the Query, and therefore that the database will grow in size, etc. and this eventually will tax the system until its usefulness is questionable. You would explain that Access 2003 is a relational database, and perhaps throw in how the relationships between the tables are governed by rules which the programmer defines. You would show how practical and dynamic your database is and how it should benefit the company and on-and-on. OK?
The System Documentation is a little more complex because it has to show the relationship of the different data types and structures and how they relate to one another: the architecture of the software, and how the parts fit together to form a whole package, capable of supplying all the needs of the organization. At this point I would tend to delegate, because it would take at least a Master Degree to explain all of this, Developer, Programmer, User, Interface Designer, they all have to work together. Microsoft hires thousands of programmers to design their systems, and so do other software companies, depending on the scope of their product.
Developer Documentation would explain Interface Guidelines and how applications software is supposed to work the the Operating System Software; Programmer Documentation might contain C++ tips (or Visual Basic in the case of Microsoft Access 2003); User Documentation contains all the how-to's for the computer operators; Interface Design is a whole subject in and of itself.
In any case, I want to wish you Good Luck with your project and Best Wishes as well. In any case, I might point out that you can show initiative at this point, by defining YOUR terms any way you want. This is YOUR project and YOU get to design the docs as well as the software. It's almost too much for any one person.
I'm here for you if you need me you can send me an email, you know.