Adding dimension to Model in BPC

Hi Experts

I am looking to add a new dimension to an existing model having transaction data.My queries are as under:

(1) Can i do it?

(2) What would happen to the existing data? Will it be allocated to the first member of the new dimension?

(3) What is the best way to appropriately allocate the past data to relevant members of the new dimension?

(4) Is creating a new model better option?

Many thanks

SAtish