On the fence,
Well, first off, Bless you for even considering living organ donation. There are many who may give it a moments thought and as quickly dismiss the idea, but fewer that actually consider it and begin thinking about testing for compatibility. Secondly, I pray for you mother and her friend, that things ultimately work out in the end and for health for both.
Based on what you've posted, you've definitely come to the right place to get multiple perspectives, a myriad of experiences and thoughtful opinions about what to do next. A good place to start is to determine the closest transplant center to where you live, look them up on their web-site and see what information they have posted for those considering being a living organ/tissue donor. Generally, the information provided there, or through other sites like the National Kidney Foundation will provide answers to most any and every question you'll come with and to some questions you haven't thought of yet.
Another dimension, and quite important one, is your own health and lifestyle. I'm no one to judge anyone, so please don't take my comments as judgmental; smoking and more than occasional or moderate consumption of alcohol is definitely a consideration with both your potential for becoming a viable donor (are you healthy enough, are there higher associated health risks to you post-op, due to your current life-style choices) as-well-as the long-term outcome for your own health, post-donation. Not only may a transplant center decline you as a potential donor, at least temporarily, but they may require lifestyle changes and demonstration of those changes over a predetermined time frame, but that is best answered by a medical screening and a professional medical determination. On the flip side, you're young, seemingly healthy and willing to make changes; all of which operates in your favor.
Of course, there is much more to the screening process than that (full medical work-up, compatibility testing with the potential recipient, screening by a social worker, etc...) and all of these processes are set up to protect you and the potential recipient.
Regarding you question about "how much changing" you'll have to do to potentially become a donor? I would offer this; most people who become donors have questions, concerns, fears and anxiety over the process and you are already on the correct first-step; Information. I wish you luck and good health and will pray that you find the answers you seek in your decision making. You'll likely have a wealth of information coming from other posters on this forum so I would encourage you to read them all and learn.
Regards!
Scott