I'm pretty well read on both Zen and other areas of Buddhism and Taoism. I have meditated extensively in the past and was also into yoga for a time, though now I only meditate occasionally (though I 'reflect' regularly!).
Not to be disrespectful but deciding that you can't be "Enlightened" when you haven't spent a prologued period of your life training under a qualified teacher is like deciding you can't do Aikido after reading books and watching videos and trying to puzzle things out for yourself.
The attitude of the Zen group you speak of surprises me as most serious meditators will tell you that Buddhist meditation is a separate issue from your religious faith. There have been plenty of Christions who have done substantial amounts of Buddhist meditation, most notably Thomas Merton who wrote extensively.
What is meant by "Enlightenment" is essentially a letting go of the various defenses that we maintain that serve to protect our constructed view ourselves from any challenge. The Buddhists have a name for people who get Enlightened without going through a formal process with a teacher. They are called Pratyeka Buddhas. It is considered very rare but it does occur. But they are considered sort of spiritual geniuses whose previous lives prepared them for their Enlightenment in this life time without the usual process of training. For most people the support of a training structure and the guidance of a teacher is considered crucial. So it would be a bit premature to have doubts about the attainment of Enlightenment before you have actually engeged in the process.
Buddhism, Hinduism, Taoism, etc. have spent over two thousand years developing their unique systems of spiritual work to produce insight. If you sincerely throw yourself into a practice with a qualified teacher (hard to find in some cases) you will eventually gain insight into what is meant by Enlightenment. From what I have read, it is almnost never what the practitioner expected when he or she started.
[Edited by George S. Ledyard on November 15, 2000 at 01:01pm]