Ahh - we had a 2 litre 2006 307, and it had 'dark sensing' headlights. AFAIK, the 'ambient light sensor', like the rain sensor, was in the windscreen. A cheap replacement windscreen would not have these sensors, but that shouldn't stop anything working - you would just have to manually switch the headlights on (& your windscreen wipers).
Non-working tail lights would be a fuse on most cars... Does this car have a towbar? Even if not, it could have been removed & sold separately. It could be worth checking whether the wiring has been butchered by fitting of towbar wiring.
As to the light control stalk - earlier 307s had problems with the COM2000 unit (housed in that stalk) and switch failures (commonly affecting blinkers), but a 2006 model car should have the later unit, which is generally trouble free.
I would recommend getting a code scanning tool - there may be useful information stored. You don't ever travel up to the tablelands do you? I am in Tenterfield from time to time, but rarely venture down your way.
Cheers
Alec