Change belt strap at V70 MY 2006- What do I have to bear in mind?

Hello together, for some time always came a flap from the B-pillar on the driver’s side. So then I drove to my to have the problem solved. He then explained to me that the noise from the belt strap / restraint system stood, and that was from the part, which tightens the belt when the overlay, so that one does not “fall out”. He then did something. The flap was gone, but the strap was always annoying, because one must pull out the belt always seaehhrr carefully And even then, he kept on acting. I was told that you had to replace the restraint system completely and that this cost 400€. In recent times, the flapping has become louder and louder. So today, I took off the disguise and wanted to spray some sticky oil into the chamber, like several times before, so that the flapping stops. At the same time, the lid is broken off. That’s totally messed up! The normal restraint function with a “normal” C At least the system blocks the belt as soon as I pull the belt back. I should try not to produce an overlay. Now my questions: Can you buy the belt strap in the accessories and then also install it myself. There are two screws to loosen and pull the plug out, right? Or does the airbag trigger? And where can I get such a restraint system? Somehow I can’t understand that because of such a “pfennig part” there s Restraint system must be completely replaced!