Electric Fireplace Insert Installation

Hello there! I'm trying to buy and install an electric fireplace insert (was looking at Dimplex Chassis 600) to cover up a hole that for some reason was made in a fireplace in my flat. I'm not sure if it's possible to enlarge the existing hole to fit a relatively thin insert or would there be any structural problems to the chimney if we tried to do that? If not we can make the fireplace shallower and build a wall around it to fit it in (like in the terribly photoshopped picture attached).

I'm thinking I won't be able to do it alone, will definitely need to hire someone but not sure whether it's work for a handman, a builder, an electrician? Also, not sure whether to purchase the Chassis 600 before I consult with someone who knows if that model would be appropriate for this, or to wait.

Any words of advice around this subject greatly appreciated as I'm really lost in all this! Thank you!

Should open up ok, do you have power supply nearby .?

Oh yes I do. Thank you!

Rather like yourself, the OP has made TWO posts in total since they joined (in MARCH 2019) - and hasn't been seen since.

And you've popped up here apparently imagining that the OP will reappear to continue the discourse.