A key point about the MediCare supplemental plans(HMOs) is that U need to choose a primary doctor.
Then he becomes the contact with the supplemental carrier and any specialized treatment is then usually done through their network.
The tough challenge is finding a primary doctor that cares and takes the time to understand your needs.
MediCare is not perfect but in my experience it does work well...
Regarding Part D for prescriptions, good idea to take this up front as if needed later U will pay some significant monthly penalties...

Just my $0.02....