Welcome to Just Answers! Thank you for giving me the opportunity to assist you! I will do my best to help!
I am sorry for your loss! You have my condolences!
You can take the IRA payments out in a lump sum, over a five year period, or over your remaining life expectancy. In any of these cases, the amount that you take out will only be subject to regular income tax. The 10% "penalty" tax that is assessed under §72 for early distributions from an IRA does not apply to distributions due to death. So all you will pay is income tax at whatever your marginal rate is.
The same goes for your dad's pension plan. The amounts you receive each year will be reported on a Form 1099-R, just as the IRA distributions would be. They also would be subject to only regular income tax.
I hope this answers your questions! If you have any more, please let me now, and I will answer them. If my answer has been helpful, please rate me highly. I would appreciate it!
Again, thanks! Have a great week!