Sounds pretty much like a daunting task, yet it has often been related to me by various practitioners an understanding of the Abhidharma teachings may help with a more nuanced understanding of later Mahayana philosophical concepts.
Yes, abhidharma is important to understanding key Mahāyāna concepts because most of the early proponents, like Nāgārjuna and others, were well-versed in abhidharma. While they rejected it as anything other than conventional wisdom and knowledge, it nevertheless formed a crucial component to classical Indian Buddhist thought. To thus understand Indian Buddhism in general you need to have read and comprehended the basics of abhidharma. As a subject of study it forms secondary roots to the original words of the Buddha.
You can easily discern who has this knowledge and who does not. Fortunately, it is free and open to all. There are no initiations required. You do not need to defer to a master. You do not need anyone's permission to read it.
1.) If you've studied the Abhidharma - why? What brought you to that point?
I was reading Nāgārjuna and Garfield's introduction discussed who he was refuting. After reading through the Chinese translation of the MMK I really realized I needed to also read Abhidharma works. The more I read about the development of Buddhism in India the more I understood the key function of Abhidharma.
2.) And more importantly, for the tradition that you uphold, how did you go about doing it?
I don't belong to any readily identifiable tradition or lineage. At the time I started I also didn't really belong anywhere either.
I simply got a hold of the books and started reading.
I've heard people who've joined Theravada groups to get a better more precise understanding. I've also heard of various Mahayana practitioners simply using the Abhidharmakosa.
is from a more Mahāyāna perspective. It is however much shorter.
There are other works and modern support material and studies available. In Chinese a lot of literature has been preserved that was lost in India and never translated into Tibetan.
3.) Has it had any affect on your understanding of the version of Mahayana/Vajrayana that you follow?
Yes, because I see what emptiness entails in the context of classical Indian thought.