Land Rover Repair: 99 Discovery II Trans, backyard mechanic, trans fluid

Question
I have a 99 Discovery II.  I am wondering if it is posible to change the trans fluid myself.  I am told that I have to suck the trans fluid out from the top, beacuse that is the only plug, it is a "sealed" unit and refill from the same place.  Is this correct?  I am a avid backyard mechanic, is this ok for me to do?  Any help with this would be great.  Also, just to say, I reciently changed the beat up air bags out with a coil spring conversion and that was the greatest change I could have made.  

Answer
Ok It's not so hard, just tell me what type of transmission? Automatic, or manual?

"Also, just to say, I reciently changed the beat up air bags out with a coil spring conversion and that was the greatest change I could have made."

Please tell me more of that, It's interesting.