Almost all the major window and door manufacturer's have CAD downloads of their products available on their websites.
As for figuring the trusses, you need to start with span, but also consider all the other factors for any floor/roof system. Start
here. Its precast, prestressed, but its a start. Look for more sites like it. Also, your school library is going to have several volumes of information on this subject, check there.
As for covering, it doesn't matter, really, you can put whatever you want as long as you can get it to stay up there and meet fire/building codes. Use your imagination, that is what architecture is all about.
There are all kinds of all-thread hanging systems to suspend anything you can imagine from commercial floor trusses. Take a look at the
Unistrut stuff.
Lastly, do your homework. If you're gonna design this stuff, you'd better
know its gonna work, not just hope it does.