I just finished replacing the king pin and bushings on one side of my car. It wasn't a hard job at all, provided you have a press and reamer. I've had the press for years, but bought the reamer just for this job. It's adjustable between 25/32 and 27/32 which covers the 20mm nominal bore of the bushings. The reamer cost $12, plus as much again for shipping, but was still inexpensive all told.
I'd say the hardest part was getting the old bushing out. Each bushing blocks access for pressing out the other, so there is no way to remove them one at a time as you ideally would like. The only way I could see to do it was to press one bushing down into the spindle and up against the other bushing, then continue to press them both out the bottom. It worked, but took a fair amount of force. After getting them out, I realized that the bore in the spindle necks down a tiny bit between the two bushing, so forcing the upper bushing through there takes some effort. It's a good thing bronze is soft. If anyone has found a better way to press them out I'd love to hear about.
After cleaning things up, I pressed the new bushings in, one from each end. That part was straight forward.
Then on to the reaming. As expected pressing in the bushings tightened them up and the king pins would no longer fit in the bushings, hence the need for reaming. After figuring out how the reamer adjustment worked, it was pretty easy to adjust it to the bushing and lightly ream it out. Of course you want to take away material slowly and carefully since you can't put it back on if you take too much. It only took 10 minutes or so and I had a perfect fit, free from binding and free from play.
The king pin kit comes with three different thickness bottom end washers to set the end play. I tried the middle one and found things still too loose, so I used the thickest.
That's the hard part, and it wasn't so hard after all. Tomorrow I'll put the suspension back together and start on the other side. I can certainly understand the attraction to sending the press and ream job to a machine shop, and if you don't have a press that's the only course. Don't try to hammer the bushings out or in - you will just ruin them and/or the spindle. But the reaming part was really a piece of cake with the right tool, and the tool is a whopping $12.