Changing kitchen doorway into breakfast bar (partition walls)

Hi, I'm getting pressure from the missus to extend the kitchen doorway into a breakfast bar.
Not sure whether this will mean making one big space, or cutting a bar area out to the left of the door from 3 or 4 foot above the ground.
I'll be getting help to do this, but does anyone know any potential issues please?
I'm thinking there has to be problems with moving cables, possibly plumbing, and the effect of probably having to move part of the wall frame.
You can probably tell from the posting I'm completely inexperienced here, any help / advice / experience is appreciated.
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