And a very nice piece of it, too!
Yes it is petrified wood with quartz drusy crystals. Beautiful piece!
The quartz drusy can be clear to smokey and it is sometimes called
"Brilliant Wood" because there is a town in northwestern Alabama where this wood is found named Brilliant.
The little pieces you pulled from inside it are also very nice looking and look to have very dark, smokey quartz. This might add to their value.
Petrified wood is not a specialty with me but I'm guessing your Dad's piece would sell for around $300.00,
but you will have to research that more for yourself if you decide to try and sell it.
Here's a link from another rock forum with more info about your wood;
http://mcrocks.com/ftr06-2/StreeterNovember06.html

Happy New Year!