Whether XP or Win 7 the install is quite easy and there are lots who can help.

You'd want to back up everything. One way that folks use (I'm old fashion and copy things to hard-drives) is they use an online back-up service. This will copy everything to a collection of machines. You access your data when you want it.

If your machine was sold with Vista it should handle W7 fine and you should have all of the drivers.

Again I ask why you want to use 64-bit OS? How much RAM is in your machine?

You could install Win 7, all of your drivers, download all of the updates, etc in 3 to 4 hours. But find some youngster to do it and watch and learn. It's no fun to get frustrated halfway through.