Yes you can change them without a press. They come pre-pressed into the upper control arm, so you just take out the two bolts holding the upper control arm and the one holding the ball joint to the steering knuckle. Knock it loose with a ball joint fork and the whole thing just slides out. Try and mark where the upper control arm bolts are though, as you need to get it close in order to get the alignment somewhat right. You will still want a professional alignment done fairly soon after doing them (within a week). I chewed through the last 20% of my last set of tires because I waited a month or so to get an alignment.
I would recommend changing the lowers, as they take much of the stress and are the more common one to wear out. You will need a press, but you can rent the kit from any auto parts store. Requires a collateral feel at first, but after you return the kit, you get the money back. You can do the lowers without needing an alignment. If you do have to do them one set at a time, as opposed to doing both the uppers and lowers, do the lowers first. You would also be wise to do the tie rod ends at the same time you are doing the uppers as changing out the tie rod ends requires an alignment afterwards. May as well save some money having to get only one alignment as opposed to two.
Here is a vid that will help you a lot.
PART 1 How To Install Replace Lower Ball Joint 97-03 Ford F-150 Expedition 1AAuto.com - YouTube
