Replacing a Dimmer Switch

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Hi all,

Is it pretty straight forward to replace a dimmer switch?
I have no electrical experience but have been watching some videos on line.
The dimmer switch for the living room seems to be faulty.  They lights keep flickering and sometimes witch off.
I don't have the cash right now to get in an electrician so was considering giving it a go myself.
My tools are VDE rated, and I would begin by isolating the power to that room.
Any advice?  Thanks
(picture not attached - couldn't upload one)