1. Create a new Relationship Query with the following criteria:
Criteria:
Deceased equals No
AND Individual Relation Deceased equals Yes
AND This Individual Is The Spouse equals Yes
AND This Individual Is A Constituent equals Yes

Output:
Name: (of surviving spouse)
Deceased: NO
Constituent ID: (of surviving spouse)
Individual Relation Name: (of deceased spouse)
Individual Relation Deceased: YES
Individual Relation Is The Spouse: YES

2. Export your Query Results.  You may now use the Constituent ID to Import and Update the Addressees and Salutations