Which shape is it?
Mine is a basic coupe but came with the sensors.
Depending on which shape megane you have the sensors may or may not have to be painted.
They are very usefull indeed especially on a coupe version..
The wiring no idea.
They use the standard beeping noise for reverse engaged , lights left on, key card still in car etc.
Fitting of the sensors shouldnt be any real problem if you have the right size hole cutter for your drill .
Mark the center accurately and use masking tape so you dont slip and damage the surrounding bodywork whether its painted or unpainted plastic.
Is most of the wiring there already? dunno
Is the sensing "master unit " in place but just not used..dunno that either.
1. get the full kit from a renault dealer, and give em your left leg as a deposit if it has to be ordered.
Seriously , it might be very expensive but if you talk to a decent "parts guy" you might be able to find out exactly what bits you need aside from the sensors.
Even if you dont buy from them.
Guessing , you may not need that much, as mine came fitted as standard on a base trim model there cant be too much extra.
2. once you know what bits you need you might be able to source them from car breakers (cars that have had front end damage).
3. another option would be
kits , maybe they are very compatible. Personally Id prefer oem equipment even second hand , cant be more than 2 years old really.
Other posters may have more detailed information
nm replies have started^ gl wi it. nb sensors are a fair distance away from the rear lights on mine.