I put in a new hot air heater a few years ago and last year upgraded the windows to double pane. Had the heater cleaned and tuned up a week ago and the shop will be nice and warm when I want to work out there.
As far as the car goes................I have those race ramp stands that cradle the tires and keep the car a foot off the ground. That way I have access to do anything under the car and it is much more steady then having it on 4 jack stands.