I'm looking to add another layer to the querty keyboard on the iPad so I can get accented characters. Can I do that?
An even simpler way to access the most commonly accented characters is to hold down that letter and you are given options.
To see what I mean, just click and hold on the letter "o" and you'll be given a lot of choices.
The standard keyboard on a USA iPad will have accented characters for e, y, u, i, o, a, s, z, c and n.
The way to do that is to add more keyboards. If you have several keyboards active, you can cycle through them using the globe key to the left of the space bar. To add more keyboards, go to Settings → General → Keyboard → International Keyboards. Pick a national keyboard that has the accented letters you want.
No, you can not modify the keyboard layout itself without jail breaking the OS. The other answers do list the existing features for accessing these characters, but I have written an article summarizing why having alternate keys on iOS isn't equivalent to keyboards with dedicated single key presses for commonly used keys.