Applying for MBA in Finance

I work in the fixed income field (trading assistant) and I'd like to at the very least find out some info on MBA programs. I would like to further my education and I think it would help advance careers. What exams are necessary to have? I graduated undergrad 3 yrs ago with a major in Finance. I've read that the GMAT is the exam that schools want you to have - do all require this? Second, do most people work and go to school at the same time? I've seen people do both and all have said the 2 years was brutal so that does scare me a bit. Other than that what else would generally be required? I've been told that having my manager write a letter of recommendation is what schools also want. Anything else?