I have all of those parts, I sadly make too much on my SSDI to qualify for medicaid which really sucks but I always try to figure out ways around things like home IV's. I have the original Medicare along with mutual of Omaha for my supplemental which picks up the 20% that part B does not cover and any additional hospital/doctor bills (saved me thousands!). I have Medco as my part D which is my prescription coverage, I get the highest coverage they allow, costs more but saves me the most in the end as I get the IV's through there (generics) at no cost. Can be really confusing, but I find that this arrangement works best as I see doctors in 3 different states (I live really close to MA, CT ) and like the freedom I have as far as finding good healthcare. I could go to Alaska for treatment if I wanted as long as they accept Medicare. I did not opt for a HMO because of this, I do not like managed care and because I have other complex issues other than CF, the original plus supplemental policy was the best fit.
You probably are okay as Medicaid picks up your meds and other services if Medicare doesn't....so you wouldn't need part D. Part B is DME, doctor's visits and home nursing care....Medicaid I think covers that too right? So keeping part A is a good thing as it is free and covers hospitalizations for the most part, I don't think there would be no harm in keeping that one.
I hope I have helped, if you have any more questions, ask away <img src="i/expressions/face-icon-small-smile.gif" border="0">
Jenn