Dimming switching

[DIYman123]

Hi, I'm currently training to be an electrician.
My girlfriends dad asked me about having a double gang switch turned into a dimmer switch, one switches the lounge and the other 2 ways up for the living room light.
Is this a straight forward task to do, of just taking the 2 gang switch and swapping it for a double dimmer switch?
I'd like to be able to impress him with some knowledge.

 

[Simonslimline]

What type of lighting is it?

Does the 2 way have a dimmer at the other end already?

Is the back box deep enough to accommodate dimmer switches?

 

[DIYman123]

Not had a full depth look at the back box, it is on a stud wall, so presume I would be Able to get a 35mm back box if needed. As for the other switch, it is just a normal one gang switch. Nothing in dimming yet.