Nice KDS-18 there, congrats.
The soap cup dispensers have a seal that rides on the pivoting shaft. The seals gets old with age and leak. My KDS-18 was pouring water out of both shafts when I tested it out in the garage with the front panel removed (I highly recommend doing this before installing). I disassembled the soap cup doors, pulled the seals out, and matched them up with ones from Lowes. Upon testing, I found that the new seals were juuuuuust a hint tighter than the originals and the doors wouldn't fully open. I disassembled the unit again, coated the new seals with Vaseline, reinstalled, and all has been good for sometime now.
There's two ways to replace the seals. If you have to do it by yourself, you'll need to remove the entire dispenser from the machine. You'll most likely need a new dispenser to door seal to go with it. If you have an extra hand, you can replace them without removing the dispenser. The cotter pin is jammed in there pretty good. The trick I found was using angle cutters and getting a good grip on the cotter pin (but not tight enough to shear the pin). Next, take a hammer to smack the cutters in the direction you want to remove the cotter pin. The soap door is spring loaded, so it'll shoot out into the tub.
I also had the same problem with the rinse aid dispenser leaking, like yours. Those seals have very odd dimensions and I had a hell of a time finding ones to match online. As luck would have it, I was able to find some from my local Orchard Supply in the plumbing department. I'm not sure if Hobart or Whirlpool stock those anymore. Let me know if you don't have any luck finding them and I'll shoot over to Orchard and see if they still have them in stock.
Lots of other info I can give you, but I don't want to discourage or overwhelm you.