[villagetinker]

There is a BIG difference between a pull down ladder ($$$) and the actual electrical retractable STAIRS ($$$$). Not sure which you after. If a pull down ladder access, the kits work very well. I have done this twice; I like a 2 man team as it makes the job a lot easier and quicker. Also, if you (or a handyman) are doing the READ THE INSTRUCTIONS and use the correct mounting screws. Finally, be sure to check the height of the existing ceiling and the working distance of the pull-down ladder, you will usually have the trim the last rung to get the correct fit.
The other alternative is to use the pull down ladder for access, and VERSA-LIFT for the actual packages. I do not recall if the VERSA-LIFT comes in a DIY system. I did look into these, but they did not offer a unit large enough for the containers for our Christmas tree, these are just over 4 feet long.