Matt, I do plan to upgrade the dish. In my experience, though, if I have an electronic system consisting of multiple components that's already working, I'm best off upgrading a piece at a time. Otherwise if something doesn't work, there's no good way to know which piece is at fault. Ideally, I'd like to upgrade the receiver first and make sure everything continues to work -- no HD, of course, but get the receiver working and programming properly activated with the same capabilities we've had all along. Then I'd do the cable (the new antenna may have to be in a different location from the existing one due to line-of-sight considerations) and make sure everything still works, then do the dish. Dish aiming isn't rocket science, but it's the touchiest part of the whole thing, so knowing in advance that everything else is working right tends to make it go more smoothly.
Thanks, everyone, for your input.