In the same state with a "garage" that was built before cars, I would first have your contractor look at and see what it would cost to do just what you are thinking of to change the car door and adding the French doors and make sure it is possible. Then I would visit the local building dept and play "would I need a permit to:_____?" I would not give any details of your long term plan but ask a step at a time. The neighbors did this just so they did not spend a lot on drawings etc just trying to get through the permit process. They did pretty much a one wall remodel and made a lot of compromises to limit time in review boards but ended up with a very nice house but still only 1 full bath (seems that extra shower is a big issue so they did a half bath instead). Two other neighbors are duking it out over similar garage conversations. One will have a sink and shower (no toilet permitted) the other will have a toilet and sink with no permit for a shower).

Depending on the cost, I intend to do a full-fledged professional conversion of the left half of my 23 ft wide x 20 ft deep garage into a 10 ft wide x 20 ft deep practice space for my very loud drummer husband who currently practices in our aluminum sunroom (bless our neighbors who have put up with him for 15 yrs! & me for having no sunlight entering the back of my house ; ). Most say I'm crazy to do this, but this is probably our forever home, Charleston is a hot market, and I could describe it as a theater room if I ever were to sell. We live in a flood zone so our house is 5 ft high. There are steps leading down to garage which is at ground level. We would begin by framing in half of the garage facade & installing a new single door to replace the current double door. Once that is done we would have the most expensive part: the concrete piers extending from the garage slab floor to support the new floor so it is level with the rest of the house. We are lucky to have a garage with a huge ceiling! Sooo back to the original question, how do I make the exterior look normal? It helps that we have a huge oak tree in front so the driveway is only a few feet long in front of where the new room will be, helping it blend. My concern is merely what will become the dead/negative/blank space. It will just be a wall of nothing but boring vinyl siding 10 ft wide and 8 ft high (see photos/it will be the left side). Thank you all so much!!! Sorry for being so long winded.

Alternately: What you do depends upon what will be needed within the shop -- amount of natural light and/or blank wall space for building storage/countertop/workspace along a wall, whether or not the size of the garage should be enlarged by extending the left end of the house. Is the front of the house facing north or south or east or wet -- will sunlight go directly into the windows and, if so, what time of day? How much natural light will shine in from other sides and is a lot or little natural light desirable? Do you want fixed windows or do the windows need to open? Is the back wall of the garage brick or the same siding as the end? Would it be desirable to move the two front garage doors to the back of the house? -- or just move ONE of the garage doors to the back wall so it is directly across from the other garage door you do leave on the front -- a drive thru garage or just a great breezeway to enable dust/fumes from the shop/garage to exit when both doors are open?

My house has windows more like this along the front, stretching almost from corner to corner and at the ceiling line to a sill height of about 66" or so. This is because my house is right on the sidewalk. It lets a lot of light in and they are high enough that there is privacy without any window covering (all you can see outside is the ceiling pretty much). And we have a great view of trees and skyline but not the cars parked right out front. A lot of people may think this does not look as nice as a full length window, but the neighboring houses with full length windows keep them fully covered almost all of the time for privacy.