Hi Antoine
If you've not used a Steadicam before and are on a tight budget, you may find a better idea is to go much cheaper than the unit you've mentioned and buy a really simple stabiliser like a Yelangu S60T (or similar). These appear all the time on ebay for 50 euro or less, and most are barely used, because people give up on trying to balance them properly! Although the gimbal bearings in these aren't usually very good, they do work okay when set up, and you will learn the basic principles involved in balancing and handling a Steadicam, and getting smooth shots. While you're doing this, buy the Steadicam Operator's Handbook (again, you might find a copy secondhand) and practise the techniques described within it. You'll only be able to do this handheld, but for many music videos, you won't be doing long takes, and you'll be developing your technique.
If you make some good progress and are keen to continue with your Steadicam ambition, keep a close watch on ebay for a secondhand Pilot HD. If you're lucky, you might find one for around 600 euro, as many people who bought them have moved on to electronic gimbals to save on size, weight and bulk. A Pilot will bring you a vest, an arm and a monitor, and that will move you forward a long way in the shots you can do (and the length of the takes). A monitor is essential for many Steadicam shots, and you want this low down so you know where you are putting your feet! You'll only be able to fly cameras under 4.5kg with a Pilot, but that covers all DSLRs and most of the lighter handicam-type camcorders.
I appreciate the system you've mentioned *says* you can mount a monitor on the sled, but you will find it difficult to achieve static and dynamic balance on this kind of device if you do so.
Hope this helps a little.