No reason to be ashamed...they were designed over a weekend and mocked up in a couple of days...engineering had little to do with their design.
To replace the spring, you have to remove the two bolts that hold the top section and the bottom section together. These bolts are through the center of the top crossmembers. The top one is held in with a star nut and the bottom with a lock nut.
Pull them apart carefully, taking care that you don't stress the plastic bushing that goes through the top crossmember and the middle of the spring. This piece has a tendency to break. I'm sure you could repair it with some good 24-hour epoxy, but who wants to do that?
Once you have it apart, flip the top section over and rest it on its pedals with the spring side crossmember facing you. Now, put the bushing back through the crossmember, then slip the new spring over the bushing and put one leg of the spring against the left bolt first - as far down to the nut as you can. Then, while holding that leg down against the nut (as well as you can), slip the other leg of the spring over the right bolt. If you get it down far enough, it'll hold on its own.
Now, flip over the top section so that it's right side up, with the pedals facing away from you. Match the bushing up to the hole in the center crossmember of the bottom section, and mate the two sections back together by pressing in a slightly forward and down motion. The best position for your hands at this point is palms down each hand on either side of the spring holding the top section's spring side crossmember.
Now you just put in the bolts, re-attach the nuts, and make sure to apply some loc-tite.
Good luck!
SOB
*edit* WARNING! Keep clear of the spring after you've mounted it on the top section...it has a tendency to pop off, and can do so even when it looks secure!
