Structurally anything is possible... just depends on how functional and nice it will look at in the end.

Not sure if it's possible, but whoever looks at the structural portion will need some sort of house design. IE: can you get the blueprints to the house?

If not, the guess work will be more from the engineer's perspective. As said previously, it will most likely take a large beam to support the large bending moment from the span of the garage while supporting the entire room. Find a friend that works with structural engineers who are registered with the state as a PE and do it for a bit cheaper. Remember you will most likely have to pull permits which also cost $$$.