用英语说：货到后一周内，卖方应提供免费的更换及安装服务

supplier/seller shall/must provide assembly and replacement services as the goods deliver within one week

货到后一周内，卖方应提供免费的更换及安装服务
the goods will arrivalled one week later,
the seller should supply with service of changing and installing by free.

Deliveries in the latter week, the seller should provide the free replacement and the installment service