Ok, so I found my ship in my Saves folder and copied it into the main Ships folder, but it seems to have crashed the program! OOps!
Not sure what you mean by Steam
I am not sure what you mean by "as long as my new save has a different name" - I can't see a Save as.. button. Only a Save button (which presumably keeps the existing name). But this is only in the VAB. Sorry.. quite confused!