Forks are a toddle, generally - but there are enough differences so that absolute, unthinking confidence can be misplaced. I went to show Terry Miller how to change the seals in his wife's super-budget SR185 Yamaha, only to find the damper rods welded - yes, by the factory - welded to the upper fork tube, and therefore without any removable fasteners. That particular set of forks is actually held together by the normally-occuring snap-ring above the seal: you pull the boot, the snap-ring, and then slide-hammer (we checked, the factory tool is a slide hammer) the two halves of the fork apart. This isn't really that different from most forks, when the bottom of the damper-rod is released from the slider by removing it's bolt above, or close to, the axle. Then the seal is tapped out by extending the fork, which means you are tapping on the seal with the interference between the lower tube bush and upper fork bush in the slider, usually. Hopefully, this will NOT hopelessly bang-up the bushings if you are planning to re-use them - wise to check you haven't deformed or burred the bushings, when you have them in your hands. This is the difference between changing the seals in your forks and rebuilding your forks, replacing the bushings in the slider and on the lower end of the tube needs to be done a couple of times in the lifetime of the bike, and it's a bit expensive compared to replacing a simple seal. The tool to put the seal in is needed because the seal goes into the alloy slider almost last, after the stanchion tube and the bushes, so a seal driver is hollow to fit over the fork tube, and sometimes split into two pieces, so that it can be used on an assembled bike after taking off the slider and changing the seal. A scrap piece of correctly sized tube works fine: long enough to go over the collapsed assembly is nice, but a shoe on a short tube will let you tap it with a hammer, and that works too, protect the tube with a wrap of plastic and find a steel or alloy tube (maybe ABS plastic woud work, too) that fits the seal nicely, and drive it home. It's not complicated, and you have one technical advantage over the professional motorcycle mechanic - lots of time to get the job done. The manual's parts diagram will show the order of the parts, and the finding and/or fabricating the tool to drive the seal square is maybe the hardest part, and you would best know how hard you think that will be... usually easy. Maybe the best tactic would be to find the seal driver before you ever start taking the fork apart: you need a fairly solid piece of tube bigger on the id than the fork tube itself, and smaller than the od of the seal you are knocking into the slider, and if you line the driver with some plastic, an old krazy karpet or something like that, you can usually get a nice sliding fit that has no chance at all of damaging the chrome surface of the fork tube, and should help tap the seal in straight, which is really what the whole operation is about.
You have to ask yourself - how many people change out their own fork seals (lots) - and how many fancy storebought fork seal drivers have you seen? (few), especially when you think about how many variations of that id/od ratio the tool has to be able to do for different motorcycles, meaning the one tool becomes a bunch of tools. Real careful people could no doubt tap in a fork seal with a hammer and punch with the washer from under the locking circlip as a load spreader... their risk of having to buy another set of seals would be increased, though. Also true you can flatten a seal, or distort it hopelessly, with a perfectly useful tool - even a pro tool - sometimes things just don't go as planned: but your chances of success with a decent makeshift driver, and care and patience, are good.
