bought mine on ebay, takes about an hour to fit.
Indeed there is a connector behind the rhs rear trim panel. Either buy a standard kit, the cut and splice into the connector, or pay a little more for a custom wiring kit and it will just plug in.
(there are only single electrics behind the panel, if you want full twin electrics it'll be a different kit)
Wouldn't worry about a torque wrench too much, just do the bolts up bastard tight. Mines been fine, towed all sorts with it.
Got mine of ebay for £60 (Nearly new), and bought ebay item 230734889547, which is the plug in single electrics. (£25). Took about an hour to fit, job done.
After using it a couple of times, I went back under and checked everything was still 'bastard tight'. There's also talk about changing the relay to upgrade the electrics. I never bothered, but then the electrics on the trailer work fine.
Gordon