Without getting into too much detail, my brother in law passed away very unexpectedly last week. While at his house to make sure everything is locked up and look after his cat (if anyone would like a new companion that likes to be around but not overly affecitonate in North Auckland reach out!) I noticed the light switch in his bedroom is not working properly. 

When I turn it on, the lights flicked on briefly but won't stay on. It's definitely the switch. I grew up in the US and have no problem replacing switches there, but have never done it here in NZ. Is it something easy (ish) to tackle, or am I going to need to pay someone to replace the switch? The power board is old style like the one on the left in the photo.

If it is not something I'm able to do myself, does anyone have recommended electricians near Brown's Bay? I just worry leaving a dodgy switch installed while there isn't someone at the house at all times to watch for trouble. 

The switch only controls one light and looks pretty standard https://tradedepot.co.nz/electrical-light-switch-single/#mz-expanded-view-692367691992

I'm trying my best to take care of as much as I can to keep a load off my wife as she's understandably devastated and not in a mental space to deal with things like this right now. Any help or suggestions would be greatly appreciated.