1.) As far as sculpting, typically, you want to use the tablet for most things. The only place where Kent recommends using a mouse (and I agree) is doing something like the grab because a lot of tablets read the lifting of the pen off the tablet and skew the result at the end. This isn’t an issue with a mouse.
BTW, when you say you can’t use both at the same time, are you saying you can only have one plugged in or just can’t hold both at the same time? Hopefully it’s just the latter, in which case, you can set the pen down and reach over to the mouse. If it is the former, though, and they plug into USB, if you only have the one USB port available, you might look into getting a USB hub which will give you more slots.
2.) If you’re in 3D view, if you click on the box icon in the lower left, you can switch it between different window types. One of the options is User Preferences. Even easier is simply to press CTRL-ALT-U (I think that would be Command+Option+U on the Mac?) and it will pop up a window with the User Preferences in it. It’s got all sorts of options in there for controlling how Blender works. It isn’t necessary to change much there, except in certain cases, but can be a way to customize how you use Blender.
