I've always found CAD programs interesting, though I haven't used them much (and I'm not an engineer). I guess some software modeling tools could be considered CAD, but not in the traditional sense. In any case, I think you've chosen a good topic for the project.

I think you have the project scope and boundaries well-defined, and just need to work out specifics. Your breakdown of the topics and how long each will take seems right to me, though of course you can adjust as you go. I also think the nature of the topic makes it well suited for illustrated instructions, since it is very graphical.

You point out that the toughest part will be choosing a particular example. My team is having the same difficulty in choosing the specifics to make it interesting and worthwhile, but doable. It's good that you identified this early and are now probably well on your way to solving this issue.

The only thing I can see that your proposal doesn't cover completely is the breakdown of the tasks; that is, who will do what part of the instructions (as well as text vs illustrations). Other than that, everything seems great.

This topic sounds very interesting.  I work with another CAD program, CATIA V5, almost every day.  While it takes nearly 1000 hours to claim that you are a skilled user who is proficient in a CAD program, step-by-step instructions help the process along to show how to do basic instructions. Since you are proposing the topic, I am assuming that you have previous knowledge about the subject matter though personal interest or classroom experience.  If so, your reference material is wide open to many tutorials and walkthroughs that have done the exact same thing that you are proposing.  Making a 25 step procedure will not be a problem at all.  Good luck with everything.  

Overall, you use a lot of effective design strategies to make your memo even more readable. Headings and bullet lists are very engaging and do even more to communicate your relevant information. Your memo is very thorough and provides two things: a relevant organization for your instructions; and, a guideline for group members. In revision, work to vary sentence beginnings and to use more active verbs. Avoid there is, it is, is, are, was, were, etc. Nice job, overall.

For group submissions in the future, have only one person submit them. And your names should both be on this memo.