Focus issues

I noticed allready a few times that my nikkor dx 18-200mm is not focussing when extended and taken close. After 10 years it is failing. So i have to go for repair . The only problem , what will be the fee for repair and what s going wrong? Even in manual modus i can t go sharp in some settings. Well somehow i like the photo even if it is not sharp. i loved the guy with the Scottish skirt.