I am guessing you are talking about buying a new car for your business? If so, the interview process asks if you have purchased a new/different car for your business, and whether you have sold a car. Proceed from there.
TT provides a fairly comprehensive business expense list, but if your expense doesn't fit into one of those categories, the interview process asks if you have other expenses you would like to enter. Click yes and add the PD expenses.
Not sure what your medicare coverage question is. So sorry.
On the Medicare issue. Because I'm on SS, I am covered for basic medical through Medicare. But the instructions are unclear and tell me to select something but I don't see any option for Medicare. Since it's not a separate plan purchased through an exchange or privately, nothing seems to fit.