Change valuation method from moving average to FIFO

We have incorrectly given valuation method for our raw materials to moving average instead of FIFO. Now, we have a lot of transactions and cannot change the method after a transaction is done for any item. I want to know if this solution will work:

1. create new database with item and business master data, chart of accounts, item groups as before

2. change valuation method of all items

3. Import GRPO, Excise and A/P invoices from old database

Does step 3 create its own JEs?? If it does, then my problem will be solved.