Modify LISTAGG query for 10g
You need to pick one of the string aggregation techniques that works with your version and supports ordering. For example, I've adapted the "ROW_NUMBER() and SYS_CONNECT_BY_PATH functions in Oracle 9i" technique from the excellent ORACLE-BASE website:

WITH a as ( SELECT t3_field1,
                   t3_field2,
                   LTRIM(MAX(SYS_CONNECT_BY_PATH(field3,', '))
                       KEEP (DENSE_RANK LAST ORDER BY curr),', ') AS agg
            FROM   (SELECT field1 t3_field1,
                           field2 t3_field2,
                           field3,
                           ROW_NUMBER() 
                             OVER (PARTITION BY field1, field2 ORDER BY field3)
                             AS curr,
                           ROW_NUMBER() 
                             OVER (PARTITION BY field1, field2 ORDER BY field3) -1 
                             AS prev
                    FROM   Table3)
            GROUP BY t3_field1, t3_field2
            CONNECT BY prev = PRIOR curr 
                 AND t3_field1 = PRIOR t3_field1 
                 AND t3_field2 = PRIOR t3_field2
            START WITH curr = 1 ),
     s as ( SELECT t3.field1 t3_field1,
                   t3.field2 t3_field2,
                   SUM(t2.field1) sum_t2_field1,
                   SUM(t2.field2) sum_t2_field2
            FROM Table1 t1, Table2 t2, Table3 t3
            WHERE t1.id = t2.idoft1 AND t2.id = t3.idoft2 AND t1.id = 3
            GROUP BY t3.field1, t3.field2 )
SELECT * FROM a JOIN s USING (t3_field1,t3_field2);


Results:

| T3_FIELD1 | T3_FIELD2 |                                             AGG | SUM_T2_FIELD1 | SUM_T2_FIELD2 |
|-----------|-----------|-------------------------------------------------|---------------|---------------|
|      asdf |      test | and_one_more_text, some_another_text, text_here |          1998 |           210 |
|     asdf2 |      test |                           text_in_another_group |           666 |            70 |


SQLFiddle here