and would there be much point getting a 64 bit version or should i stick with a 32 bit??? i have spare ram i can put in with a 64 bit os
It all depends on the software and hardware you plan to use. 32-bit drivers will NOT work under 64-bit windows. Therefore, if you have any hardware that doesn't supply 64-bit drivers (either for Windows 7 or Windows Vista), then you will want to avoid 64-bit. The same goes for any software you have that might be old. Many old software installation programs used 16-bit installers to install 32-bit programs sometimes, so the installers will not run under Windows 7 64-bit.
If you plan on going above 4 gigs of memory, then 64-bit is what you want. Going 4 gigs with your current setup should be good.
However, if you do GO go 64-bit, you CANNOT do an upgrade if you're running Vista 32-bit. You will have to do a complete reinstall of the OS and your applications. Just be sure to use Easy Windows Transfer within Windows 7 to backup your user account profile and files before you do this. That way, you can easily put them back under Windows 7 when you're done installing it.
If you are upgrading from Vista 32-bit to Windows 7 32-bit, then you can do an in-place upgrade of the OS.
If you are currently running XP, then you have to do a full install whether it's 32 or 64-bit Windows.
Hope that helps!