Data Loading in Purchase Cube After Data Source Enhancment

Dear Experts,

I have recently enhance my standard data source extractor 2LIS_02_SCL with 11 fields.

Now we have to load data for last 3 years. We are using   2LIS_02_ITM, 2LIS_02_HDR, 2LIS_02_ACC 

data sources in Purchase Area.

I am doing this activity for the first time. What strategy i should follow in order to perform this activity?

My concerns are:

a) Do i need to load the extracted data from setup table to all used datasources??

b) Will it impact the delta process of other data source??

c) While loading the data will their be any record mismatch for records olders than 3 years and changed recently??

Thanks

Sumit