I think for the first few times, you should just go out and just ride with the moto driver. The quality of motor pacing is highly dependent on the moto driver. A good driver will be able to accelerate smoothly so you don't get dropped and will slow up on the uphills and speed up on the down hills
Does the moto has a roller bar so you will bounce off the moto rather than crash into it?
You gotta find someone who has experience; find a coach who has done it before. Don't get your friend, who has a Katana, to help you! Finally, do some research and find out what the local and/or traffic laws are, in regard to motorpacing, I know CA cops will ticket anyone, if they catch them, motorpacing riders.
I'm not sure motopacing would be that helpful for cross. Granted, any workout is helpful in some way, no question, but for cross you'd probably gain more doing a different type of workout. The only people I've met who regularly motopace are Cat 1/2 road racers.
It can be extremely beneficial - but it all depends on what you want to work on. You can use it just as a high speed drafting workout at whatever pace you feel is appropriate - tempo,threshold, vo2 - or you can use the motor for 'active' recovery and come around into the wind for periods of time at a much higher intensity. More than anything, much like a group ride, it's very motivating to have that motor setting the pace.
BUT, as others have said - you'd better have an experienced driver and work out communication methods (speed up, speed down, pothole, stop, etc) before going out. This is not for the inexperienced and can be very dangerous if you are in areas of traffic or not used to bumping off the back of the scooter.