Help me assist my father in getting benefits

My father is 85. He served in the Army on a tug boat and was exposed to at least trychloroethalene, who knows what else. He got out, went to college and went back into the Navy reserves for another 30+ years. Despite fighting 5 differant kinds of cancer (bone, melanoma, leukemia, lymphoma and prostate) it never occurred to him to file a claim with the VA. He also has hearing loss and bruxism. These are just the health issues that I believe could be service related, I'm sure there are more. What is the best way to help him file a claim? At his age, I want to make it as easy and straightforward as possible. Is it best to hire a company to help him or a lawyer? I'm going to be as involved as I can but I live several states away.

Will the VA do anything in regards to the cancer since it's all been treated and is currently in remission?

Thank you!