I just replaced my entire rack in the drive way, along with the outer tie rod ends. It took me about six hours, but a certain un-named parts store sold me a bad outer which I had to return, then go to another store because they didn't have a replacement.
To your question - it is certainly doable to replace the bushings in your driveway. I don't know if you'd have to pull the steering column shaft and the outer tie rod ends to give yourself enough play to get it off of there. I suspect you'd at least have to pull the steering column shaft. That's one bolt, so it's not hard.
As a preliminary test, I would pull the nuts off of the two anchor bolts, then shake the p!$$ out of the rack to see if it moves. If not, the bushings probably aren't your problem. I'd also shake the tie rod ends to see if they're loose. If so, I'd buy the parts and do the whole thing. I've had tie rod ends come loose - trust me, you DON'T want that to happen, even at low speeds.
Auto Zone sells a Ford logo rebuilt rack for about $180, and the outer tie rods are about $12 apiece. The rebuilt rack comes with new bushings. BE SURE you follow their instructions for stretching the teflon sealing rings for the hydraulic hoses.
I suspect you'll need to have it aligned if you replace worn bushings. I believe you can get the bushings standalone from Auto Zone or NAPA. Good luck, and let us know if it worked out for you.