I would not go for the 64bit version to be honest, the support isn't very good for 64bit at the minute. For example you have to do a bit of work to get flash working on it, and there is also some aplications that have not got 64bit applications out. Try the 64bit on a live cd first to see if it does what you want and everything is working. If not go for 32bit it has far better support.
As for motherboard drivers, you shouldn't need them. Once the installation is finished everything should be working automatically without doing anything. Ethernet, sound etc will all work out of the box.
What you do need drivers for though will be a graphics card if you have one, like all applications in ubuntu you dont need to go scaring the Internet to find them, if you go to administration>hardware drivers it should auto detect the best drivers for you and you can install from there.
Then once your up an running go to the ubuntu software store in the menu to install all the applications you require.