I'll admit, the quant will be a killer. But it also depends on what kind of learner you are. If you're the Deep-end-of-the-pool type, then learning by doing might actually work. I'm also assuming that your finance concentration in MBA exposed you to a decent enough level of stats.
rsvoss posted in the "Quant maze" thread stickied on top of this forum about what kind of quant might be expected for each discipline, which I will shamelessly steal and post:
1. Accounting. Stochastic differential equations.
2. Finance. Stochastic differential equations.
3. Human Resource Management. Differential calculus.
4. Management. Differential calculus.
5. Management Information Systems. Differential calculus.
6. Management Science. Differential calculus.
7. Managerial Economics. Differential calculus.
8. Marketing. Differential calculus.
9. Operations Management. Stochastic processes.
I'd recommend you take a look a the thread itself, which is full of very good advice.
At the *very* least, you'll need to be familiar with the regulars of research methods: factor analysis, regression analysis, SEM, etc...