For what it's worth, I finally got it installed.
I tried running the uninstaller for the old software, since the installer seemed to hang before it got to any "installing". Sure enough, the old uninstaller hung as well. I force quit it after about 5 minutes, and then retried the installer. This time, it worked.
And this driver does in fact fix all of the bugs that have been bothering me. So now I'm a happy camper, because I can print in draft mode.