I much preferred the 68k style of assembly over x86 just feels cleaner and nicer to work with but as Eric said, you have an x86/x64 machine so easier to play with.
That said in the modern world it is far harder to get to the metal than it was when I played with assembly so getting an old machine emulator and using that would be a good in.
For a gentile introduction in playing at a low level you could explore the old nerd classic that is http://www.corewars.org/ is is a pseudo assembly language where two programs get loaded into an "address space" and have to locate and destroy the other before they get killed
Its not that hard to kick an asm function even from x64 code, the only thing that has gotten hard is that the C++ compiler no longer allows for inline ASM.
Is a good series on getting started with x64 asm in VS2010, he shows you how to call an asm function and then moves on to explaining what all the instructions do.
I learned ASM on a 8088 like board with MASM as the compiler this looked so much like x86 asm that moving to PC was only getting used to the new register names like EAX and stuff.
The other thing you can do is write a simple function in C/C++ and see what the compiler transforms that into on PC in a debug build. You will want to do this in a debug build because in that case the compiler will actual transform all of your code in to ASM.