The Windows 7 disc will contain both 32-bit and 64-bit versions, and if you have an upgrade edition then the licensing allows you to switch to 64-bit Windows 7 even if you were previously running 32-bit Vista.
BUT there's no supported upgrade installation that will convert a 32-bit Vista system to a 64-bit Vista or Windows 7 system. The only way to get from 32-bit to 64-bit is via a complete install from square one.
It's six of one or a half-dozen of the other as to whether you do this by installing 64-bit Vista from scratch and then upgrading it to 64-bit Windows 7, or by just waiting until you have a copy of Windows 7 and installing the 64-bit version of it from scratch.
I would contact the manufacturer to ask about the availability of a 64-bit OEM version.