How do I verify the uninstall of Grid Control and WebLogic?
Be really, really careful when mucking around in /etc/rc.d/; this is where your startup/shutdown programs live, so removing the wrong file will put you in to a world of hurt. (Unfortunately, I can't tell you which file is the one Oracle tends to use.) 

Second, Oracle's uninstall instructions always leave a lot to be desired, as does the actual process, which leaves just about everything hanging around on the file system even when it isn't necessary anymore. 

For removing Grid, IIRC (that is a big IF), I think you're in the clear -- pretty much exactly what I would have done. And, as to weblogic, same deal -- I'd have run the uninstall.sh and see what happens. I suppose you could nuke the entire directory at this point so that there'd be no chance of an old file coming back to bite you, so that'd be just about the only other thing I'd do.

Good luck with the re-install...