which frameworks(MVVM light, Prism, MEF,..) should i use for my Financial Silverlight application?

first of all, I am new to silverlight(play around with it for one month) and this is my first job. However, i am willing to learn anything which can let me advance my silverlight knowledge.

Currently, I need to implement a big Silverlight project about Financial(kind of similar to Microsoft Accounting). It will have a lot of tables from database.

Because it is too big, scalability and maintain are pretty important.

Can anyone here tell me which silverlight framework i should learn and use (MEF, Prism, .....)? Time is also a constraint so i don't think i can learn all. Plz advise me the best one.

thank you