Unless I was using a similiar color and the original paint job was a really good one. But from what you said, it sounds lke the original job wasn't so good. I would lightly sand the surface, make sure it is clean, use a high quality primer, then topcoat (2 coats.)
Remember, a paint job can only be as good as the preparation. If you paint over a drip or a roap, you'll have a freshly painted drip or roap. Take the time to prepare carefully and the final job will look great.
There are some essential tools, in my opinion. A five-in-one painter's tool scrapes, smooths, opens cracks, makes coffee, and gives a great backrub. A putty knife and joint compound or spackle to fill in any holes or dents, and high quality paint and brushes. Don't skimp on materials - you're saving enough doing it yourself to buy high quality stuff.