Hi Charly,
If you are uncomfortable changing out the disc, then you should find someone who will change it out for you. From a purely physical standpoint there is not much to it; the information is in the database, which can be found here at this forum. You need to save your files and also re-install the operating system, unlock your plug-ins, and some other stuff that I can't remember right now.
This is where a Mackie authorize service center can be your best friend because they know how to do this stuff in their sleep. Sometimes they have to read the service manual, but they also have one to read.
I am confident that I have changed many harddisc units in more than a few machines, including the d8b. By the nature in which you asked your question you might want to look for someone to do it for you and set the mixer up correctly.
So the longer answer is yes. if I may be so bold to speak for some other members, most all the people on this forum have had success in changing out their harddisc (over here where I live we call it a hard drive... same thing). It is pretty easy to do but if you get "in there" and not know what you are doing, there is a chance you will damage something else.
Hope this helps,
Michael
PS: I just saw your post Peter. Some folks are not mechanically inclined and do not work well with these things. It is like when someone has never blown a horn and when they pick it up you run the other direction because it sounds so bad... why would I expect someone to sound good. Just because I can make an instrument sound good doesn't mean everyone can. Just saying and not trying to start up anything.