Firstly, you may want to see a Sports Doctor, Physical Therapist and/or a Podiatrist.. Tell him/her about your injuries (past and present) and see if they could recomend a goods sneaker for you. As silly as this sounds, this may have been the reason why you needed to drop out.
If their are no tears showing, start with the elliptical. First a normal pace to see how you feel. Stay on it for as long as you can. Week 2 set your goal to 30 minutes. Week 3 you'll want to shock the bod, so after the first 10 minute warm up, do minute intervals going as fast as you can for one miniute, then slow it down (NOT stop) for the next minute. Interval training is great for building cardio.
If your gym has a Step Mill (not stair master), that would be a great machine too. The Step Mill is like walking up an escalator backwards. After a few minutes, it really kicks your ass. Definitely start with the elliptical. It mimmics running with low/no impact.
After a month, try the tread mill again. Start slowly so you don't reinjure the area. If the tread mill works out after a week or so, go to the track. If the track works out of then move to the street.
I also joined late at 35 and 3/4 through, my achilles started bugging me. It's still not right today, but they'd have to strap me down and carry me out with just 2 months left. My achilles still isn't right today (3 years later)