Yes, you sure can! It's not that difficult. I worked in construction for many years, and I've done that on many houses, even on exterior walls. You need to use posts and beam, they can be either wood or steel, I've done both. You just need good temporary supports while you do the work. Be sure you get it engineered by someone that knows what they are doing and get a permit if necessary. If you hire a contractor, always make sure he's licensed and bonded!