uncleb
don't rent a car, there are no places to park. use public transportation or a cab.
i think anyplace you stay in manhatten will be very expensive. i have heard a breakfast of ham and eggs sent to the room can cost $35.00. better to eat at the many local deli's or small restaurants.
keep a hard look on your face, and if someone stops you for anything, he or she are probably up to no good. new yourkers don't generally talk to strangers. if you need directions go into a store or ask a cop.
the subways and busses will get you almost anyplace.
new york is a fast paced, fascinating place, but walking the street at night should be done in well lited areas.
i think a trip to the observation tower of the empire state bldg, 109 stories up, or the observaion tower of the rca bldg, 86th floor and out doors, as i recall, is a must.
times square at night is something to see.
i don't know how long you will be there, but like any trip, plan on the things you really want to see and the feel of NY will be there all the time.