Help of a form with a pre-select field

I am struggling (still new to the tool) with this:
I want a field that is a select distinct result set. This will populate a select list.
Once the user has made a selection, I want to populate a form with a number of fields with a further resulting query (a further select on the same table with a qualifier (the value in the select distinct).
Also, based on who is logged in, I want to make the form (except for the select distinct) to disable CUD functions and become read-only.
Finally, I want to have a grid display based on a select on another table using the same qualifier from the select distinct value. (I expect this is another form, that will be linked to this one; just not sure how to set passed variables.)