Your story is amazing and inspiring - well done for living through such a difficult time! If you can do that, you can do anything!
I personally love the elliptical - I need low-impact exercise and I find that I can go on that thing for 30-40 minutes without ankle joint pain that I get from a lot of other machines. I'd definitely suggest giving it a try, start slow and move up from there. I also echo almeeker's advice about the rowing machine- I love it!
I've got about 70 pounds to lose too - with patience and persistence, you'll get there. Good luck and welcome
Female, 30 years old, 5'4 1/2" tall
Starting weight 1/4/11 = 215.2 lbs.
Weight 8/30/13 = 179.8 (net: -35.4)
Current mini-goal: 175 lbs.
Lowest weight: 156.7 lbs.
150.2 lbs. <--- Official "Healthy BMI" weight
Estimated final goal: 130 lbs.
"You don't have to change your life today. You only need to change your day today."