Hi Teresa,
I have run into similar situations where our list values have been modified and documents using older values need modified. Without knowing what those older values are, the only way I have been able to accomplish this is by querying the repository database directly.
To get a list of all the metadata fields using old list values I would perform the following queries in the repository database:
Find the property id for the metadata list field in question:
SELECT * FROM propdef where prop_type = 'L'
I'm looking for our list field called 'Section' and see that it has the property id of 49.
I can then use that id (49) to return a distinct list of all values used in that metadata list field (from propval table) while removing any values that are currently configured in the metadata list ( lup table). Resulting in all the old list values that are still used in the repository but not currently part of your metadata list.
SELECT DISTINCT str_val FROM propval where prop_id = 49
and str_val not in ( SELECT list_val FROM lup where prop_id = 49)
Results can be used to run manual searches, queries expanded to return document lists, or put into a workflow to automate document changes, etc.
Hope that made a little sense and helps!