I got approved on my first attempt back in 1999. I was pretty much bedridden with lyme, but had just lot my job 3 months earlier due to being too sick to work. If you have a good dr. that will explain how sick you are and that you can't work you should be ok, but I know others have not been as lucky as I was.
As for how much you will get. That all depends on your situation. It depends on how long you have worked all your life and put into social security. It depends on if you are married or have dependents. If you are single you can expect less than $1000. Every year it usually goes up as cost of living goes up, but not by much, maybe $20 or so each year. They will tell you and you will get benefits going back from when you applied. It can take up to 6 months to get your first check, but the first one is a big one as it is about 6 months worth of payments.
I wouldn't count on the income as enough to live off of. They don't ever get you that much, but with disability you can get other benefits like food stamps, heating vouchers for free heat during the winter. There are other programs available too once you are approved that will help.
Hope that helps some. Good luck.