"...is there any official data, documented studies, etc. etc. on essential oils out there?..."
Essential oil books are a lot like soap making books -- a girl has to kiss a lot of frogs to find a true prince. Many of the books and internet info about essential oils and their use are honestly not very creditable. Even if there are kernels of truth in these books, so much is drivel, it's impossible to sort out what's what. It's kind of depressing, because I've bought a fair number of these books, hoping to find some real meat to sink my mental teeth into ... and I keep finding the same tired stuff time after time.
There is some good news. There is increasing body of research that documents the therapeutic effects (or lack thereof) of essential oils. Although there is no single "be all, end all" source for this information, Robert Tisserand does a very good job of keeping up on the current research and debunking the foolishness and misinformation that abounds in the aromatherapy world. He just published the second edition of his book, Essential Oil Safety, A Guide for Health Care Professionals, ISBN: 978-0-443-06241-4, that I would recommend getting if you have the funds (about $75-100). He has a website
http://roberttisserand.com and a facebook page
https://www.facebook.com/RobertTisserandEssentialTraining He presents webinars, seminars, and classes around the world.
Here's an interesting blog entry from Tisserand about a famous incident in which early aromatherapy researcher Maurice Rene Gattefosse used lavender EO to successfully treat gas gangrene in his burned hands:
http://roberttisserand.com/2011/04/gattefosses-burn/
As far as finding a good source to buy the essential oils themselves, it's really tough to KNOW without a shadow of a doubt who's reputable and who's not. I look for this type of thing -- What people are encouraging sound research into the uses of essential oils? Who is contributing to fair and balanced discussions with the public about essential oils and about safe, sound uses of EOs for health and beauty? Who is making an effort to educate consumers without a lot of drama, pressure, or hype? Who is putting themselves and their good name out in the public as a source of reasonable information? What businesses provide detailed information about their EO products and provide a wide and varied selection of EOs for consumers to choose?
I could ramble on at length, but instead I'll close with a few information sources that seem particularly creditable and have been helpful to me:
Robert Tisserand:
http://roberttisserand.com
Nature's Gift, Marge Clark:
http://www.naturesgift.com/infomenu.htm
Aroma Web, Wendy Robbins:
http://aromaweb.com/
University of Minnesota
http://www.takingcharge.csh.umn.edu/explore-healing-practices/aromatherapy
National Center for Complimentary and Alternative Medicine (National Institutes of Health):
http://nccam.nih.gov/
And a person can search for research data using PubMed (US National Library of Medicine):
http://www.ncbi.nlm.nih.gov/pubmed/
I'm sure there's lots more, but I hope this gets you off to a good start! --D