HI,
create service in AC01 transaction or add this in under service activity via cj20n project builder
if you want this service code in sales order then you have to use item category DIEN.
DIP profile you can assign in project profile this is linking between PS SD
Under Transaction DP81 project/wbs or inquiry would be link with each other such check inquiry there might be option for putting wbs as account assignment.
Regards,
Sanjeev