Cost Loading in P3

the first I suggest to login to this site and be a permanant member, it will help you very much,
in response your query, I can summeraize my comments as follows:
lumpsum contract usually have a price/cost breakdown and this breakdown come in table and define elements of cost of project including engineering, procurement, construction and so on, if bidding be a completted package, it will certinally be in package, based on this table you should develop detailed price and input in P3.
I hope the above is clear.