So I got to work this morning (with a fresh mind) and after a bit of googling figured out my problem in 30 minutes. Basically it boiled down to adding a reference to ORACLE_HOME in the bash script itself, and the full path of SQLPlus. After that, things ran fine even with changing the permissions of the scripts and related files back to normal and running Nagios with the Nagios user.
One of the 'nice to haves' for this little monitoring things I'm working on in Nagios is graphing capability - so we can see trends of the performance data at a glance. Just before I left today, I discovered that Nagios might install with this capability commented out. I let you know for sure in my next post.
While I was working on solving the graphing problem a different way, I got focused on some graphing addins for Nagios that required perl modules I didn't have. I learned that cspan is basically like 'yum' for perl. Didn't know what it was before today. In fact, I haven't had any exposure to perl before this project. It's all good - learning new stuff every day.
I also learned a big way to correct my golf swing today. I need to grip hard with my left hand and the right hand is just for support. I was driving much better and more consistently after I made that adjustment.