How do I convert a garage.....
Also the slab will not be level, garages are sloped toward the front so any water getting in will drain out.
Also probaly lower than the rest of the house
Might consider having the floor built up with screeds and plywood to get it level, and even with the adjoining rooms.
In addition to Willie's comments (above), consider that a garage 'conversion' is pretty hard to execute well. For one thing, you have the driveway leading to the 'family room'. Also, it oftentimes doesn't 'flow' very well with the house's floor plan. And not to mention, what to do with the CARS!
Not to try and talk you out of it or anything--just some things to consider. It may not be the wisest use of your remodeling money.