Flag records based on service date

Please see attached excel file for sample data.
I want to mark records from the same customer as Index / ReIndex  (in the service_type column) based on the following rule:

Flag all records with svc_order =1 as 'Index' in Service_type column.

If customer_id is same
and svc_order>1
and DateDiff in days (svc_start_date for previous record where svc_order = svc_order-1, same customer_id) <=30

Then Flag it as Re-Index.

Attached sample data in excel file.
service_Type column will be initially null and updated as mentioned in the above logic.

How can I accomplish this using sql?
Index-ReIndex.xls