hh, "difficulty" is relative because people have different levels of mechanical abilities as well as access to tools. Most, people, if they take their time and follow the plans carefully can do it, those who feel that they don't need to follow plans and can jump around steps to save time usually do not end up with a working frame/slide.
Most finish up 'rough' though. But because yours will be a dedicated .22lr frame, I think that you will have more leeway.
Get the one that's almost finished (80%?). Even if it doesn't work out, you will probably have spent some fun time and this knowledge will contribute towards your next build.
Try looking at this site:
homegunsmith.com