I just purchased a used Summilux-M 35mm f/1.4 ASPH from the NYC Leica Store. I got it for a really good deal, basically $1000 off. For some reason it seems to be a bit greasy. Also the glass looked like it had a smudge and I used my lens pen to clean it. It then greased up the front element. What should I do? Return, or just clean? If clean what do you guys recommend.