In desiring to do such a major overhaul, it is often suggested to start with the 'smallest' thing -- the one that will be easiest to implement.
Maybe something like 5 or 10 minutes twice a day, of positive visualization and/or affirmations? Maybe seeing yourself taking a walk or doing a yoga class?
I know it sounds ridiculously tiny...but it does start to recondition your subconscious and your body & conscious mind do tend to follow.
I hear you about the alcohol. Can you see your way clear to replacing one bottle a day with something like a sports drink or green tea or something?
The thing about getting into volunteering too soon is that it feels all like we're doing it for someone else - we make the effort and someone else benefits. It can feel more like a drag than a good thing, at this stage.
So, it likely will be more inspiring and self-motivational to start off doing things that you feel you will be there greatest beneficiary.
Or. You could just say, "HEY!!! surgngnl...get off your butt and start doing something, anything, just one thing."
But our conscious and subconscious minds tend to resist those types of orders.
Best of luck. You've passed the first major hurdle in any event...you are feeling the desire!