Lowercase username option (patch included)

I've modified the stable version of user_import (5.x-1.3) to include an option to change all username characters to lowercase. It seems to work OK on my Drupal version 5.3. I'd be happy to submit my (first) patch (ever), but frankly I don't really know where to start...

I read some of the handbooks on the subject, but somehow that info doesn't really seem 'applicable' to me.

I realize this might not be the right place, but since it's a patch for 'User Import' I'll submit it here anyway. Please excuse me if I'm an annoyance. I've created the patch with Winmerge. It affects 'user_import.new.module' and 'user_import.install'. Hopefully somebody can take my patch and 'fix' it, so it can be reviewed.

Thanks in advance!