Really need help

Basically I bought a g66 raider of eBay and I didn't like it so I returned it. Then the seller only returned me half of the price of the laptop( 499£) I asked him why is that. He told me that it calmed damaged the lid which the monitor was in was bent and scratched a lil bit (Full back assembly) And he says it's 500£ to fix the problem . If someone could help me or give a link to not used full back assembly I will appreciate that. Here is more info Laptop:MSI GE66 Raider 15.6" 360Hz - Intel Core i7-12700H - 16GB - 1TB - RTX 3070 Ti