The door locks are not that hard to replace. Although replacing the inner door panels will need some re-glueing which is a messy job and looks rubbish if you do it wrong.
The ignition lock is a nightmare (and I've been working on cars for 28 years). If you think about it the manufacturers don't want someone to easily get at the ignition lock do they? In case someone wants to steal the car.
The hassle involved in replacing the lock barrel in the steering column is beyond you if you don't know how to rebuild a car with your eyes closed. I'd pay the �170 at the dealership and buy a new key.
The cost of new locks would exceed �170 anyway and thats without any labour charge. Your ignition key may also have a transponder chip in it. This is an electronic security device embedded in the key which talks to the dashboard and allows you to drive the car. If you don't have the four digit transponder code (usually within the cars handbook), Renault will need your car chassis number and will charge you between �50 -�100 to give you the code.
Sorry mate.