This is certainly a fine line to walk. On the one hand, storing calculated values can actually be dangerous and cause real fiscal damage if actions are taken based on invalid information. With a spreadsheet, the calculations can be expected to always be current but not so in a database because there are multiple ways to update a record and if you don't properly perform the calculation every time the record is updated, then the calculated data might not actually reflect the underlying parts.
Is this more dangerous than a spreadsheet where the calculation on row 40 might be different from the calculation on row 20?
I prefer calculating values in queries because I believe that is the lesser danger. Or, if you are using A2007 or newer, you have the option of creating a calculated column. This is limited functionality but will work OK provided all the arguments come from the same row. But since you can't ALWAYS do the calculations this way, it can be confusing to the user and rather than have them learn two methods, I think it is better to teach them one method.
The best thing you can do is to build in some instructional material. Create forms and reports that explain certain technical aspects of the app and how to use them for other purposes or how to copy them and change them. Having a beginner help you with this will go a long way towards targeting the explanation to the level of a beginner. But there is still no getting around the problem that whomever will take this database over will need a certain clarity of thought to grasp the technical details. A database created by a beginner would be full of patches and work arounds and just plain bad choices but a database made by a professional should provide a clean framework that new features can be added to without disrupting the whole app.
When I create databases that I know will be owned by non-professionals, I frequently make conscious decisions to dumb down certain functions to make them easier to understand. Slick is a dirty word when you are developing for non-professionals. Simple is always better.