Parking is challenging, but there are parking garages in the area that cost $15-19 a day. The museum is wheelchair accessible, but I did not notice on site availability.
Parking is difficult in this area. I would definitely recommend traveling by train to the Smithsonian Station or using Uber/Lyft if possible.
Parking garages about a ten minute walk or use uber depending on your timed pass the big b hop on and off tour bus
If you are staying in the city use the subway system. If not parking garage is your best bet.
Wheelchairs are available at the entrance on 14th and Madison. There are a limited number available, so earlier is better. Parking is difficult though there is street parking. Parking in the Reagan center is usually reasonable and isn't very far. There are also a number of colonial parking garages around the area
Public transportation
Street parking is available. I do not know about wheelchairs.
Thanks! Your answer is awaiting moderation.