A "yard" refers to length - I think a bolt of fabric is generally 40-50" wide. As has been said, some bolts come wider, which allow you to do it with a single panel - vice a seam down the middle, or two seams dividing the panel into thirds (which is still workable - especially with some patterns - and it opens up options for you.)
I'd suggest using a fairly lightweight cotton or cotton blend (cotton duck comes to mind for some reason...) and washing it before you install it. 3M77 should keep it up there for a good long while.
Reemmber, no-one's telling you to use a pattern or not - or what pattern. I'm still waiting for my wife to settle on something, but I think (since we're going to paint it blue anyhow...) that the 89 Limited is going to end up with a "night sky" pattern - and it may even have luminous stars!
When I redo my 88, I think I'm going to see if I can get an interstate map printed to order, and use that for a headliner... I do a lot of driving.
Just because you got a solid colour from the factory, doesn't mean you have to put another one in... Have fun!
5-90