The truth of the matter is that if you do not feel any vibration or pulsing when applying the brakes, your rotors are not warped. However you may still have glazing, hot spots, or excessive grooving of the rotor surfaces which will prevent the new brake pads from seating properly. That will reduduce braking power and reduce the effective brake life. That's why most shops will require the rotors to be turned or they will not warranty their work.
If your rotors only have minor grooving and the depth of the grooves do not exceed the thickness of a business card, you do not need to have the rotors turned. You can save money if you do the work yourself, however you need to be able to judge the condition of your rotors and diagnose other potential brake problems. This can only be done with some experience. Other problems often overlooked by inexperienced home mechanics can include sticking calipers, cracked hoses, or broken and missing hardware like clips, springs, etc.
I agree that brake service can be a fairly simple task that most home mechanics can easily do, however I always recommend that you have an experienced friend or neighbor assist you the first time, preferably someone who has done more than one or two brake jobs themselves.
The $150 prices you have been quoted are actually very reasonable. Many shops will advertise lower prices to just to change out the brake pads, however they will alway recommend more work than just changing pads and you end up paying more than $150.
...Rich