TR,
I agree with everyone above about the floor jack and jackstands. And never get under a car that is only supported by one thing. Example - if the whole car is up in the air on 4 jack stands put something else under there to catch it if it falls. Many people put a couple of wheels under the frame rails, or leave a jack or two under the car in the raised position, not carrying any weight, but raised to the point where they're touching the frame and will catch the car if it falls off the stands. The first time you see a car fall off stands or a jack you'll know why this is so important. Another popular thing is to get yourself a used railroad tie or other large piece of wood and cut a couple of lengths to whatever size you need.
As for changing the oil, you don't have to get your whole body under the car, just your head and one shoulder. I have two, 1 foot long pieces of wood, 2x10's, and two 1.5 foot long pieces. I place the shorter pieces on top of the longer pieces and drive the front wheels up onto my "ramps." It's perfect for oil changes when I don't want to take extra time to put the car up on jackstands - and you don't need any extra room to store a couple of foot long pieces of 2x10. A 6 foot 2x10 should cost less than $10 at Home Depot or Lowes. If my ramblings don't make any sense, just let me know and I'll snap a picture for you.
Semper Fi,
Culprit