Finding my Grandfather, Where to Start

Hello all, I am relatively new to genealogy searches and have encountered a bit of a conundrum. My maternal grandfather passed away when my mother was around 8 years old. I don't have a lot of specific information, just anecdotes from my grandmother and mother. I know that he was a Vietnam veteran, a marine, but he lied about his age to enlist, making dates harder to get correct. He was also Hispanic, and some of the documentation has been anglicized.

I know that there is a records request option from the VA, which I have sent to my mother and grandmother, but who do not have a desire to acquire this information. I also have no idea if his service dates would fall within the 62 year window for archival records, though I have submitted a request. When I have asked my mother and grandmother for information such as SSN, service number, or service dates, my mother has said she does not have any documentation and my grandmother says its "probably in there somewhere" with regards to her storage, which I do not have access to. I've come to understand that there is an emotional component that my mother and grandmother are carrying that I believe is contributing to guarding information regarding my grandfather.

Ultimately, my end goal for this is to connect with people who may have served with him, to help form a better understanding of who he was or what he experienced.