32 Bit & 64 Bit

Hello

I'm going to purchase Vista. I have a AMD Athlon 4800+ Processor. It's dual core. Does this mean that the processor is 64 bit or 32 bit?

32 bit, single core?
64 bit, dual core?

Should i get Vista that supports 64 bit (if thats what my processor is) and would it make my pc run any faster?

Thanks