How can I fix my power shower switch?

My mother-in-law pulled the pull cord switch on my power shower so hard (thinking it was the lightswitch!) that the string broke in two. I re-tied it but it won't work - she's obviously used enough force to break the switch mechanism inside. On opening up it looks like spaghetti junction. Do I need an electrician or is this a DIY job? Can you buy parts, and is this gonna cost much? (Triton T80si)