The program I use here at Purdue is supposed to be like SolidWorks, but it's called IronCad. It's a very temperamental program which loves to do crazy stuff on you. Just last night, part of my part got sucked into a "black hole" where the modeling kernel just threw up its hands and gave up, and any time I tried to move another part near there, it would also disappear until I rotated the view. Very annoying, that IronCad. Luckily, I only have to deal with it for another few days because next week is finals week. Autodesk AutoSketch ought to be a good solution. I recieved some training on an old version of that back in high school.
When you assemble my horn, make sure you attach the bracing pieces to the outside of the horn flare panels before you attach all the horn flare panels together. Otherwise you can't get at the places you need to put screws in.
I'd suggest waiting until there are computer-generated plans.