Go with the telephone poles for your pilings. Buy them yourself so that you can pick the ones you want, and not all are treated the same. Ideally you want a newer pole treated to your suiting, and putting that on to a contractor often results in the whatever one is lying there.
What is the labor rate - hourly or for the project? $3500 seems high as it sits, but how many workers and how many days is the estimate? You can run the math and see the breakdown.
Quite frankly you might only need someone to set the pilings. Use SPAX bolts for your framing, hot dipped galvanized fasteners, and T-25 torx decking screws. The first page here has some step photos of our dock I built (the pilings were already driven into place):
http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=433065&page=1
