partition tables

[BigP]

Hi All , We are thinking of converting one of huge table in to partition table .  What is best way to achieve this ? Is there any alter table clause that can do this or I will have to export ..recreate table with partition option and then import . Also how can I mentiod that partition should have only 100000 rows . For example after each 100000 rows add another partition ? If I have 10000000 rows in the table , should I expect some performance gain out of this   Thanks , BigP