Have a look at the photos on http://www.berlektrolin.de/gruendermaschine/
Whilst not in English, photos will give you an idea of what to expect when undertaking such a task.
I would really recommend with a machine of this age really stripping it down to parts and giving everything a good clean in an acid bath rather than just running descaler in situ. So there is no need to worry about scale getting stuck in the steam wand. In any case you can take the steam wand off so no problems there.
Its a big job if youve never attempted such work before. I bought a Brugnetti machine aged around the same (made in 94 I think), I was relatively surprised at how little scale there was in it.