Thank you for giving me the opportunity to assist you. I will give the best answer that I can with the information provided.
I am sorry for your loss.
If your uncle's estate was less than $1 million dollars, there would be no estate tax consequences at the MD or Federal level (federal amount 5 million).
There is also no inheritance tax for your aunt as in Maryland, property passing to widow or widower is exempt from MD inheritance tax. There is no federal inheritance tax.
Presuming that your uncle passed away in 2011, your aunt will file a joint return, as a surviving spouse for the year 2011, during 2012 tax season (Jan-April 15th).
She is probably on Medicare, but may need some type of other personal insurance if affordable---if paying for uncle's coverage after a year is not an option.
Here are some publications and websites that may help:
Survivors (tax considerations):
Info from AARP about Medicare and Insurance:
Policy search for Medigap (supplemental insurance)(this entire website is helpful)
Medigap buyers guides and info:
Here is a good article and resources for personal finances for widows:
I hope this gets you started! Please let us know if you have additional questions.