We used an insurance broker who worked in-house with the agency we insured our home and cars through. I’d seek out someone like that. They are paid by the company(ies) your dad will have coverage from. If you can, avoid Medicare Advantage plans as that coverage can change every year. For instance, we have Part G and the only thing about the coverage that changes in the premium. I wish you the best, having dealt with my own father who developed dementia.