Gradient/Header help

[chilllax]

I am trying to make my first custom skin but I have run into a problem. I created my gradient in photoshop and saved it as a gif with the same dimensions as the default gradient but when I uploaded the new gradient instead of having the stretched look it looks tiled?

I made my header and I am happy with the way it looks but I cant figure out how to do 2 things.

1. I want the length of the header to run the length of the navbar. I can get kind of close by messing with the image size but I can never get it exactly right.

2. www.halogrid.com/hgforum/index.php How would I go about curving the corners of the white space behind the header like in that forum.

Thanks for any help.