In answer to your first question, no there is no single button that will do it all for you. You need to know what you want erased so that you don't erase things you (or Windows) need.
The time it takes to erase depends on a few different factors, such as the amount of data that needs to be overwritten, the speed of your CPU, the amount of RAM (memory) your system has, how many times you are overwriting the space, and any other programs running at the same time. With 64 gigs, 3-6 hours for a single pass is not unusual, depending on the system.