How do I replicate the iOS keyboard appearance?

I have made a custom number pad keypad for my iOS app, but want it to more closely mirror the appearance of the standard keyboard. I am looking for advice on how to make a standard UIButton look and act like the standard keyboard buttons.

Specifically, I need to figure out the following for the iPad and would like to do as much as possible in an xib or storyboard.

The size of the buttons
The color of the keyboard background (or even better, how can I determine this myself?)
The background color of the button
The font and color of the text in the button
How do I add the shadow under the button?
How do I have the button highlight with the grey color instead of blue?
The spacing between the buttons
How do I keep the "group" of buttons centered as a whole when changing the orientation? (all of the resizing options anchor it to a side and not to each other)

Do the standard buttons use images, or do they modify standard UIButton's? Or more appropriately, which is better for us to do?

UPDATE:
I have created a project for the number pad which is a complete working example. However, I have not spent much time on the actual appearance, which is what this question was mainly about. I have posted it on Github and made it an open source project (covered by the MIT licence, so commercial use is allowed as well). Hopefully other people will find it useful, and hopefully others will feel inclined to help make it better and look more like the native keyboard. The Github repository is at:

https://github.com/lnafziger/Numberpad

If you want to do it mostly in IB, then the following can be done:

Size
Colours
Background Color
Font
Text Color
Shadow (to UILabel's not UITextArea)
Spacing
AutoSizing

There is a cool PSD vector kit for all types of iOS elements that should help:

http://www.smashingmagazine.com/2008/11/26/iphone-psd-vector-kit/

Anyway, to the rest of the answers:

Size

Take a screenshot of the buttons and determine the size in Photoshop, or you can use CMD+i on the image file to see the pixel dimensions. Remember to use CMD+Shift+4 and then drag (and then Space to make the screenshot).

Colours

Use the DigitalColor Meter app that's preinstalled on the Mac, it's pretty cool for all kinds of functions.

Background Color for `UIButton`

The actual UIButton will have a background color of [UIColor clear], however, for the whole keyboard background, it would be best to create something similar in Photoshop and again using color pickers to get the right gradients. Then you could drag this into IB as a background image.

Font

Again, have a look at fonts/try Helvetica

Text Color

[UIColor black]

Shadow:

Programmatically:

[text setShadowOffset:(0,1)]; // One option
[text setShadowOffset:(0,-1); // Another option
[text setShadowColor:[UIColor whiteColor]];

But, you can also set the shadow in the IB inspector for a UILabel.

Button highlight

Look at the UIButton reference http://developer.apple.com/library/ios/#documentation/UIKit/Reference/UIButton_Class/UIButton/UIButton.html

Spacing & Rotation

If your using IB, then you could just drag on the buttons to whatever location.. IB has some autosizing options that determine where the buttons are spaced according to the TOP, LEFT, RIGHT and BOTTOM. You can also set if they are stretchable or not.