To replace a break line is pretty simple, The Carriage return is represented by CHAR(13), while the Line Feed is represented by CHAR(10). You can use the following example replace method to do it.
REPLACE(REPLACE(REPLACE(FIELD_VALUE, CHAR(13) + CHAR(10), 'something else'), CHAR(13), 'REPLACE_VALUE'), CHAR(10), 'REPLACE_VALUE')
Note: The FIELD_VALUE is the original value that you want to replace with, this is usually the column field. while the REPLACE_VALUE is the value that you want to replace with.