Just a few things to watch for on 156's.
Check the Cam belt has been done, it needs to be done at about 30K to 45K, not 60 as the service manuals say. Uneven idling is quite common, it's a throttle actuater problem easily fixed. Watch for worn suspension links and bushes, occasionaly steering Rack's seem to fail.
Selespeeds can be troublesome, it's important the car has had it's various 'Campaign recalls' as these fixed some of the software glitches. Do a search on here for 'selespeed problems'.
Be carefull with the spec of the Car a lot of 156's a parallel imports, nothing wrong with that, but not all were to UK spec, and the Trade marks them down when you trade in. The buggers don't sell them much cheaper tho.