we had garden view room and were basically as far away from the tower as we could be. we loved it! it was so quiet, looked out side our room to all green and water, no other buildings, parking lots, people or noise! we could see the electrical water parade thingy come by each night just 20 feet outside our room.
yes, it is a walk to the main building and it is not connected so at some point you do need to go outside. if i recall correctly, the outdoor part is covered. we tended to just go outside from the door closest to our room and walk by the lake, pool and then into the main building as it was more direct than going inside thru the hallways.
as for adding time to your walk to mk, it made a 6 min walk maybe a 12 min walk, not a negative for us when we valued the privacy, view and quietness more. we would walk over and watch the fireworks either from the stairs of the tower or the front lawn. can't beat that view!!!