Yes, you need the works and it will be costly. Front shifter, front and rear derailleur, 118mm bb, and new cranks. Have you considered going to a 12-27 rear cassette with the double crank. That is alot cheaper ($35), and maybe a longer chain. It will give you a 39 inch low gear (39/27). The lowest triple gear inch would be 32 (30/25), assuming you have a 25 maximum now on the rear.