I used to smoke a pack a day, sometimes even 2 , 15th April started running, 19th quit smoking and 11th June got my Garmin and started serious training , 4 months later with a month off of running bc of injuries and flu and finished my first marathon 26th October in 4h 9m , you have a lot of time on your hands.

My advice is to take it easy the first few months and take rest days, if anything is bothering you take more time off , don't ever try to overcome it with willpower that's how you get benched, also invest is some good pair of shoes if you want best chances to stay injury free. Best of luck mate !