02-03-2014 06:30 AM
Make sure your lookup is those 5,000 contacts.
Click Edit | Replace Field
Choose in "Replace contents of" the ID/Status field, and type or choose "value" that you want to replace with, assuming you want the same value in all 5,000 records.
It will replace on all 5,000 records, whether there is already a value in that field or not.