I know this is for SQL2005, but in SQL2008 you can do this:
select name, object_definition(object_id) proceduredefinition from sys.procedures
Now that you have a procedure definition request, I would use it as a view (I will call it T1 in the example below)
select name, proceduredefinition, replace(proceduredefinition,'texttoreplace','withthistext') as newcodedefinition FROM T1 where t1.proceduredefinition like '%something to search for%'
Now copy and paste the new code definition into SSMS and execute.
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