Ok. First place to start is to take the camera outside into bright sunlight and shoot a few pics at a high contrast object. Something with bold black lines in white works well. See how the focus looks. You may be trying to focus in too dim a light or the contrast might not be enough, or.... Too many variables and autofocus is extremely easy to fool.
If that focuses ok, then start working on your studio to see what you can do to get more contrast or brighter light to focus with.
As to sharpening, unless you can set your camera to sharpen the images, you're going to need to sharpen them in photoshop (or another editting program) before you try printing your iamges. Now, IMO, it's much better to not sharpen in camera and do it yourself to the amount an image needs (they aren't necessarily all the same.) If you shoot RAW file formats, you don't have a choice as the camera doesn't sharpen the raw image, you'll have to sharpen it during conversion or during editting.
My workflow goes from RAW to photoshop. Then I do any editting, color correction etc. Then I resize and finally I sharpen as the last thing before I print or save for web use.
Hopefully that helps a bit. [img]/ubbthreads/images/graemlins/smile.gif[/img]