600 dollars is to much for now I can do a little work to the exsaust side my self with out a problem would this do to open the up and could I then still use the same cam but make up a little more power
Yes, you will make more power. Probably about 10-15 more horsepower out of a decent port job.
Yes, you do need a different header that is GT40P specific. FMS makes the only shorty style header that will fit the P head. BBK and MAC both make a P specific long tube header.