SQL script to replace server name in HTML Reminder emails

We currently use images in our html emails.  The html points to the images which are held on one of our servers soon to be decommissioned.

Rather than updating each reminder & assignment individually accross each process, the preference would be to run a SQL script.  LANDesk support have supplied the table/column names (lc_value on lc_action_value) that we need to update however, my limited knowledge of SQL 'replace' statements is the problem.

What I bnelieve to be the replace statement is below, however, I believe I need a substring to specify the table/column. 

Update lc_action_value SET LC_VALUE = (replace('servername','218','246'))

GO

Any suggestions, much appreciated