How to replace 32-bit win7 into 64-bit?

There are a lot of beginners asking me, the 32-bit flagship version win7 is installed in the computer, and the computer memory in the home is 4G. It is said that changing to 64-bit can improve performance and ask how to replace it?
In his opinion, 32-bit is replaced by 64-bit, just the change of numbers, it seems that just change the 32 in the system to 64.
This view seems ridiculous, but as a newcomer to the computer, many questions are very simple. In fact, the difference between 32-bit and 64-bit systems is not only the change of numbers, but the difference of the kernel.
Therefore, if you want to replace 32-bit win7 with 64-bit win7, you need to re-install the operating system, just like replacing xp with win7 is the same reason.