For question # 1.
Your image should have 3 parts: base image (background), normal button, selected button. (In that order) For me, it usually helps if all three parts are of equal length. Also, for the life of me I can't get anything but a bitmap to work.
Now, when you first set the object type to taskbar make sure all your settings are set the way you want it. *If you're going to use a fixed size make sure to set the width in the summary tab when you're done.*
Next, go to States > Appearance. After browsing for your image, click on the 'Advanced' button.
Take a look at the example image and apply the explanation to your own image. I've put the two images together and you can see the how the margins look in Photoshop with the guides and pixel rulers.
A = The left margin of the base image (the background of your taskbar). It will usually be anywhere from 2-10 pixels in from the very edge.
b = The right margin of the base image. Again 2-10 pixels in from the right edge of the base image.
c = Where your normal button image starts; the very edge.
d = The left margin of your normal button image; 2-10 pixels in from the left edge.
e = The right margin of your normal button image; 2-10 pixels in from the right edge.
Once you've determined all that, you can then input the information into the marked fields. (See image above)
A = Left margin of base image
C-B = Distance between the right margin of the base image and the left edge of where your normal button image starts. (Probably anywhere from 2-10 pixels, depending.)
C = Where your normal button image starts.
D = Left margin of normal button
E = Right margin of normal button
So if your taskbar image is 300 pixels wide, and each image is 100 px (base, normal, selected), you'll wind up with something like this:
a = 10
c-b = 10
c = 100
d = 110
e = 190
Lastly, set it to 'stretch'.
Apply and check out the results. If you take the time to get all the parameters correct you shouldn't have to do much adjusting and re-adjusting. But if it's not appearing correctly go back, review your image sizes, calculate the parameters, and make the adjustments.
Hope this helps.
