Mike has some solid points on this topic.
my .02, having laid a dozen or so lawns over the years..

you don't need to add anything on top of the soil if you have a good finegrade, but if not, some mulch/dirt will help it grow faster. most nurseries will deliver for free if you are ordering 2500sqft, but if you have fencing up, will only leave in the driveway. get 5 friends for a total of 6 and have 2 bring wheelbarrows. work in 2 man crews, one wheeling and one laying. you can do a lawn of this size in 3-4hrs tops. if you order the pallets all at once, lay it in a day. the longer it sits, the longer it takes to green up and "take" in the dirt. mike is right, no foot traffic or pets for 2 weeks. water 2-3x daily and keep wet. I'd recommend renting a lawn roller. only $20-30 for 1/2 day and roll when done. it'll make the seams less noticable and smooth any high spots.
imo, $100 and a couple guys that wait in the home depot parking lot go a long ways. legal or not, they are not going away and if it saves your back and makes the job quicker, do it. having learned the hard way, doing it yourself is just plain crazy, especially with cheap labor plentiful. hire friends for beer or hire "those others" for cash. you will be thankful in the end.