For the Blue Sky Music tutorial you may be thinking of the Solution Recipe that we used to have for eCart. This is still available in the archived documentation section of the eCart support page.
Other than that it is just the tutorial and the sample files that are available from the download center.
In regards to getting the insert working properly you can have a select list that is populated from a recordset that selects all of the id's. If you would like to display some of the info from the users table for that user you can submit the form with the id selected and have a recordset that is filtered based on that value. You would then have access to that users details from this filtered recordset. You can just add them into any part of the page by expanding the recordset and dragging the value to the desired area or use the bind or insert button to apply the value to a text field.
This page would just be a basic insert into the staff table. You may want to do one more check though before you insert the new id, you should have another recordset that selects all from the staff table where the person id matches the currently selected one. If the recordset is not empty you would want to stop processing and return the user to the page with an error message saying the record is a duplicate one.
As for having the text field and select list that part is doable but you will need to customize the insert server behavior to check to see if the text field has a value, if it does then use that value, otherwise use the value from the select list for the personID.
This may not be as straight forward or as easy as you hoped it would be but it is all doable. If you have any questions about any part of this please let me know and I will be glad to get you pointed in the right direction.
