How exciting that you have ordered a thermomix, you will love it.
A good piece of advice is to keep using it for a couple of weeks, initially you may have some failures, just peresevere and all will be well.
This forum is always good for help and advice.
I have 2 slider boards from different sources. They are not really necessary as long as you remember not to drag your machine without them as it will effect the scales. I prefer one of mine over the other but existed for about 8 years without one.