There is excellent info on trackball bearing replacement in the comments of this:
[https://sean-the-electrofreak.blogspot.ca/2010/05/mini-project-fixed-my-trackball.html|https://sean-the-electrofreak.blogspot.ca/2010/05/mini-project-fixed-my-trackball.html]
Which also refers to
[https://translate.google.com/translate?sl=ja&tl=en&js=n&prev=_t&hl=en&ie=UTF-8&u=http%3A%2F%2Ftorapo.com%2Ftrackball%2Fmicrosoft%2Ftrackball-explorer.htm&act=url]