Uh, oh -- does Lightroom require a version of Photoshop CS2 with the 3.x version of Camera RAW? Because 3.x Camera Raw will not work with Photoshop CS1 -- which is what I've got.
It's a standalone product with its own built-in raw processing. The controls are similar to those from ACR. It costs nothing to try and will give you a good idea of where you want go in the future.