There is a fair bit to be lost, i havent weighed everyting i have removed but saved 35kg from just the rear of the car, seats, rear cards, isofix bar etc etc. Plus with yours been a 182 and not the cup you will stand to lose more than that. Front seats weigh an abosolute ton! The cup drivers seat is like 25kg alone, so i imagine the 182 half leathers are around 30kg. As for removing the roof lining, you might aswell if going all out but if your gonna leave front door cards and dash in, prob not alot of point taking roof out only weighs about half a kg and is a bit of a b**ch to get out.