Interesting interview. Thanks for sharing.
While I don't know much Tibetan (in the future I plan to study it intensely when the conditions allow), I translate Chinese and have found that above all else when translating anything related to Buddhism you need to know the vocabulary and jargon. The grammar in Classical Buddhist Chinese texts is normally rather simple with the word order being primary (this in contrast to Indic languages where conjugation, declensions and cases are key), though all the technical vocabulary needs to be understood both in its Indic and Chinese contexts (in the latter this often varies according to the time period as well). In the treatises by natives you see vague allusions to the Chinese classics which for educated native readers is readily understood, but for someone like me I found I had to read many of the Confucian classics to firmly understand the meaning.
Translating is a highly educational experience. You really get into the meat of texts and come to understand every little feature about them.
It is also a humbling experience when you see all your past silly mistakes, or when others point them out.