All excellent posts and good advice. Here is my 2 cents from my experience.
Khenpo Sonam, in L.A., as mentioned above, is a very jolly and serious young Lama near you. He is clear, kindly and speaks good English. I've personally met him and he is the real thing. I trust him as a working Lama - someone you can work with on a regular basis.
If you are serious about LCNT then you may want to contact the organizations of HH Kyabjé Dodrupchen Rinpoche:http://www.mahasiddha.org/
and or HH Kyabjé Yangthang Rinpoche:http://vimalatreasures.org/yangthang.aspx
to obtain the Yab Shi empowerment from one of them, if at all possible. They are the same as the Omniscient Longchenpa. There are also many other highly qualified Lamas who can give this empowerment.
You have to ask around. Certainly I would mention Venerable Gyatrul Rinpoche, Tulku Thondrup, or any of the Palyul Khenpos for LCNT Teachings and empowerments.
You also should keep your ears open for a Yeshe Lama retreat which usually requires that you finish your Nundro first, but I think sometimes is given if you promise to finish your nundro.
The Yeshe Lama is the practice compendium of the LCNT and is a short path - path. http://www.shambhala.com/yeshe-lama.html
Again, you have to keep your ears open and ask around.
Drs Anne Kline and Harvey Aronson are qualified Western Teachers of LCNT at:http://www.dawnmountain.org/content/teachers.html
Anne has the unique ability to translate the LCNT prayers into proper English that also fits the traditional melodies.
I highly recommend Dawn Mountain as an excellent source of the authentic LCNT lineage.
I believe that their current Teacher is Venerable Adzom Rinpoche who is the same as the wonder-working Longchen Rabjam.http://www.whitejewelmountain.org/rinpoche.htmlhttp://www.berotsana.org/sangye-khandro/
Is an excellent source for the holy LCNT and I think you might write to her for suggestions.
She is one of the translators or the Yeshe Lama and certainly one of the most qualified Western practitioners of LCNT, and it is a delight to hear her melodious voice give Teachings.
In India there are several places of study and practice for LCNT.http://www.khenchenrinpoche.org/2-college.htmhttp://www.palyulsg.org/
among others.http://www.amazon.com/s/ref=ntt_athr_dp ... evancerank
lists 12 translations of Venerable Longchenpa.
Of course the modern Dzogchen Master, Chögyal Namkhai Norbu Rinpoche, while mostly teaching from his own original terma cycle, also holds the tradition of, and teaches as, the incomparable Longchen Rabjam.http://dzogchencommunitywest.org/?page_id=2
Hope this helps, and please forgive any mistakes or omissions as I am getting old, lazy and forgetful.