How do I - Update the SharePoint Search Service Application Default Content Access account credentials using Powershell

When corporate security policy require that account passwords be updated, the Default Content Access Account used for the Search Service Application needs to be manually updated as well.  If your Search Service is in a funky state, this might not be possible using the browser UI.  When this happens, you'll need to resort to Powershell to save the day using the following script:

$userid = "domain\search_account";
$password = "account_password";
$ssa = Get-SPEnterpriseSearchServiceApplication "Search Service Application";
$sac = New-Object Microsoft.Office.Server.Search.Administration.Content($ssa);
$sac.SetDefaultGatheringAccount($userid, (ConvertTo-SecureString $password -AsPlainText -force));

Enjoy
C