Haha, there is really no “conversion” process for any Eastern spiritual traditions. It is a way of life, less of a belief system - so if you have the right “view” and practice the taught techniques with dedication, you are a practicing Tibetan Buddhist. Unlike Sutrayana-based S E Asian Buddhism, or Mahayana-based Zen and other schools, Tibetan Buddhism, while being Buddhist in terms of metaphysics, is more shamanic in nature due to techniques from Bonpo, Kashmiri Shaivism, etc., and hence transmission is key from a capable teacher, be it Mahamudra or rDzogchen. While I have been studying rDzogchen practices for a long time, my primary practice is Kashmir Shaivism (Krama school).
As for my teachers, there are several - Chogyal Namkhai Norbu, Lama Jigmé Namgyal, Khenchen Namdrol Tsering, Mingyur Rinpoche (Mahamudra), Tulku Urgyen Rinpoche amongst others.
Reginald Ray of Dharma Ocean offers pretty accessible teachings (some as digital courses) which are good enough to make a lot of progress. Advanced work such as dark retreats, Tögal, etc. does require some direct physical guidance of a teacher, however. Allan Wallace is another good and accessible source.
The one thing I did benefit tremendously was a somewhat different world growing up - where I could travel extensively at a manageable cost, backpack to places, just stay in some remote place in the middle of nowhere and learn from obscure teachers, etc. I guess that has become more difficult in the present world, but thankfully, more digital resources are opening up. So I think it is just a matter of time before more Teachings become better accessible (though the Lamas are cautious about sharing some teachings as without a good level of mental and energetic maturity, self-harm is a possibility). With China’s aggression in Tibet, the one benefit is that a lot of these closed teachings are now much more accessible due to Tibetan refugees migrating to other countries.