basics on User Defined Functions

Is this the correct way to return values in a record from a UDF in 7.4.+ ?

Is it ok to modify the arguments as in 'arg_int'?

-- return type should be RECORD
--
CREATE OR REPLACE FUNCTION test_function( int )
RETURNS RECORD AS '
DECLARE

arg_int ALIAS FOR $1;

var_record_out record;
var_message_out text;

BEGIN

var_message_out := ''This was successful'';
arg_int := rg_int * 3;

SELECT INTO var_record_out
:arg_int AS intX3,
:var_message_out AS message;
RETURN var_record_out;
END;
' LANGUAGE 'plpgsql';