I just got a Mercedes Benz SLK 2008 280. I was just wondering if the Keyless Entry feature is standard on that model. Regardless, also I wanted to know...how do I use a the keyless entry feature? Also, I wanted to know...how would I know if I had the keyless entry feature...like what physical apprearance and where would it be located on the car?

If you already have the car then you would already have the keys which MEANS that you should already know about the keyless entry since there is no key on your keys. Genius....

For some reason I feel as if you dont really own this Benz......

Actually, I think you referred to the Key that was given to you when you purchase the car. The mercedes key would have a key in it at the back and you can actually pick it out with a small slide button and use that key to open the door of the car. Oddly, though, you can't start your car with that key. You can lock and unlock the glove compartment with it though.
The key given to you has the remote function that you press and unlock the car, as well as open the trunk, this is called keyless entry if I understand it correctly.
Otherwise, in the S class they can give you a card that once you keep it with you, and touch the car, the car unlock itself. If that is keyless entry for you.