I got an amazing deal on a “for repair” Elgeet 13mm f/1.5. The problem with this lens is that the focusing mechanism is nearly frozen. Aperture works great. I was wondering if anyone had a diagram or instructions on how to open this lens and replace the old grease? Also, what are things that I need to be aware of when I open a lens? I have never done this before. Lastly, what kind of replacement grease should I use? Thanks!