DIY is fairly straight forward if you want to do a paving stone / brick patio space. The large cost is going to be labor and then the material. If you plan on doing it yourself you can save a ton of money.
It's actually pretty easy.
- Mark off area and remove sod.
- Put down a layer of sand and make sure everything is level.
- Edge area if desired, then lay pavers in a visually pleasing pattern.
- Dump some sand on top of bricks and use a broom to sweep it into the cracks.
- Wet down bricks so sand settles.
Pick up a Patio and Decks book from Big Blue/Big Orange and have at it. You can get paving bricks pretty much at any DIY/Home Improvement shop but it would be cool to find reclaimed brick from an old building that may be coming down in your area. Free too.