To answer your other questions:
If you install the OEM version you WILL get updates.
32bit v 64bit
The Windows most people have currently got is 32bit, and the CPUs most people have currently got are 32bit.
BUT you can buy 64 bit processors, and install 64 bit Windows.
But I would not recommend it.
64bit Windows requires 64bit drivers, and most hardware does NOT come with 64bit drivers.
In think in 3 or 4 years time most PCs will have 64bit CPUs and run 64bit Windows, but at the moment you are better off sticking with 32bit.