OK. I just went through this mess about a year ago so I'll try to be as helpful but brief as possible!! : )
When you start receiving Medicare, you get part A automatically, but you have to sign up for a part B plan, which covers doctors visits, labs, etc. For example, I have Pinnacle which is my contracted payer for part B. Now, these plans as well as part D vary by state, so I would recommend going to www.mymediare.gov and there you can see what's available in your state and what type of coverage you can get.
Same thing for part D (I hear HealthSpring and SilverScripts are good plans), you have to pick a plan that best meets your needs. The monthly premiums and co-pays vary wildly.
Just a quick question. Are you also receiving SSI in addition to disability? I know that because I get the SSI and I don't make enough money per month, the government basically pays most of the premiums for my parts A,B and D, although then I didn't have a greater choice as to what plans I could pick.
Also, there are special procedures and stipulations reguarding Medicare paying for insulin pump supplies and home IV care. If any of these apply to you let me know and I can post the info or PM me!!
Hope this was helpful, sorry it's so long!