>So, the question : Has anyone done this ( Rick ? ) or does anyone know of a CAST() that would get the GUID(16) into UID in one go ( and perhaps give me some hints about how to incorporate that knowledge into an SSIS package )

If you specify the data source as a query, use the following for all PK/FK fields:

cast(LEFT([GUID-16 field],8)+'-'+substring([GUID-16 field],9,4)+'-'+
substring([GUID-16 field],13,4)+'87D9-9DE36423D459' as uniqueidentifier) as [field_name]

Basically, adding the dashes and tacking on the missing 18 characters on the end. Then it casts properly. Since you're using the same string to pad it out, all PKs and FKs will still match.