Like everyone is already saying, the price totally depends on what you want to do. I’d write down in as much detail as you can what you want and get a few people out to give you an estimate so you have some idea on price.
As far as which is more stressful….they are both stressful. We are going through this decision ourselves except ours isn’t remodel or move; it’s add on or move. For me I think finding a house that we want, selling, buying, remodeling (I don’t think there’s any way we’d find a house that meets our criteria that is turn-key), and moving out/in seems more challenging so I’m really leaning towards adding on. We’ve remodeled the whole house in stages while living in it so I know what to expect there. We’re planning on living here during the addition construction, just moving into the areas of the house that are not being worked on. If the entire house was being remodeled all at once I’d probably want to find a place to rent for a couple of months.