New Year's Resolution - Get back to running

My best friend is 50 years old and has a chronic disease (asthma) that has been affecting her life for the past 5 years or so... she was on prednisone (amongst other drugs), a steroid medication, that made her gain a lot of weight (and she is naturally skinny)... I watched her suffer for years, struggling to take a breath or coughing so hard at times that she would break a rib... but last summer her doctors were finally able to manage her condition and she's been feeling better since... she also started training at the gym and doing some cardio on the treadmill to improve her lung capacity... well, I guess she liked the running so much that she set a goal for herself to run a 5K in September, which she did! Then she wanted to run a 7.5K and she did! On Dec 31 she ran a 10K and now her goal is a 1/2 marathon and then a full marathon! My friend! the 51 year old mother of 3 with a chronic disease and a full time career (who is also writing a book)!... so while I was listening to her her telling me about her 10K victory and looking at how happy (and great) she looked I was thinking: "if she can do it what is stopping me?"... I used to run, in fact, I started running when I was quitting smoking 11 years ago... every time I had a craving I would go out power walking and after few weeks I started running... then a bad knee injury prevented me from running for 2 months and I lost interest. (did I mentioned I have ADHD and lose interest and motivation quickly :)) .. over the years I'd do some running as part of my training but not consistently... but now that my friend is running, I am inspired too ... Deep down in my wildest dreams I would like to run a marathon with her... but I am not sure I can with my bad knee (still hurts if I overwork it)... so i am not going to set that as my goal.. For now, all I want is to run at least 5 days a week and run a 10K in the next few months... and then I will reevaluate my goals... At this point, I am running on the treadmill and I can run 5 km by doing 10 min intervals with walking breaks of 60 seconds or so... So, please, all advise and tips are welcome, including training programs, readings, gear, nutrition, etc. etc... oh, did I mentioned that I am 41, I have two kids (a 2 year old and a 20 year old who is still living at home), a husband, a full time career with a crazy schedule... we moved in a new house in Sept 2009 and has been renovating and decorating since... we try to keep our social life active by going out and entertaining...