There are 2 plugs on the K46, one is a vent and the other is a filler plug which is flat on top. I just changed the oil in mine at 53 hours. To remove the filler plug use a sharp knife or box cutter, but you just get it under the edge of the plug enough to pry the plug up. Once removed there is a round coin looking magnet on the inside of the plug, clean it. Be very careful putting the plug back in with the magnet. Use 5W50 synthetic motor oil. On another tractor forum there is a write up with pictures on doing the oil change - search for K46 oil change and you should find it. Also if you pull the K46 out and change the oil be sure to release the parking brake - don't me how I know
The write up RBLapham is referring in the other forum (PM me if you need to know name) is located in their John Deere stickies section at top of their JD lawn and garden forum. It's an excellant 'How To' post.