I installed one a few years back on my Grand Am. You are correct that you have to oil it. If you keep the car long enough, it pays for itself because you can clean and reoil the K&N filter as opposed to replacing it. IIRC the K&N was about $45, but that was a while ago.From what I understand, the only thing you'll notice would be a change in the way the engine sounds. Throatier, I'm told.
The filter must be oiled, if not done properly you'll encounter sensor issues. Again, so I'm told.