There is no more work involved than any other WC apart from the fact that it is concealed if that's what you meant?
If there is access via a shelf or panel, then it is no problem. Most of them in a built in frame are serviceable internally so you only need access to the tank from the front or top. Roca access is behind the flush buttons panel on some models but you may need a bit more room than just that.
I don't know the make she is having obviously but if you look on Roca UK website, you can see the type of thing I mean.
If it is just a concealed cistern as in, one you wall mount and box/panel in then it is a similar story but you would need access to the side or bottom connections too. The ones in a purpose manufactured frame are pretty well sealed as a unit from my experience so there are no externally hidden connections to worry about.
Hope this made sense?