Roller assembly wheels broke off

I removed the old shelf which had the roller assembly built into it, for the drawer below. I placed the new one in, and then realized that the new one had no glass shelf. Easy enough, I though, just pull off the old one. At that point, I realized the old one was held on with 2 plastic pieces, one on each end. The front one was easy to remove, and the glass then slipped out easily. But, the back one, was not so easy. It was a little like a chinese puzzle, needing to be lifted and twisted in just the right way, with a thin screwdriver or knife, all the while one slip or overtorque away from breaking. You then had to remember exactly what you did, and do it in reverse in order to get it onto the new frame. Easier, but not easy. There were 2 other seals than need to be moved from the old frame assembly to the new, before it could be installed. I guess I'd like to see instructions for making this switch included in the box, and for the price, it should come with new plastic pieces and rubber seals, vs. having to use the old ones. Not including the glass, I get, but the rest surprised me. Either way, most capable people will be able to do this, just keep the above in mind, and take your time with that back plastic piece.