MK4 2.0 Petrol - Buying Advice

Hi

I am thinking about a Mk4 2007/2008 143bhp petrol engine in Ghia (90k) or Titanium/X (77k  miles) form.  Both have partial service history, scuffs and scratches but not that tatty over all.

1) The 2.0 Ghia, had a flat battery when the dealer started it and after that the display was showing engine fault - was this to do with the flat battery or a sign of something worse?

2) Am I correct in assuming these are chain driven?

3) Is there anything I should be looking for in particular mechanically; the 2.0 Ghia seemed to lack a bit of "go" compared the Titanium/X I am looking at (flat battery issues?), but other than than both seemed to drive OK.   Our other car is new and small which is fine for most things so looking for the Mondeo to be  a "run about" that take larger loads and also on occasion cover longer distances.  I opted for petrol as I have read these are more reliable than the diesels variants and cost less to fix.  (I had a MK1 Focus petrol saloon which wasn't too expensive to repair and best of all it didn't need much maintenance!)

4) I am looking to replace the standard sony radio/6cd changer with an aftermarket sat-nav jobbie (seems to be several around) - any recommendations as to which is best any implications for the interaction with the drivers LCD screen in the Ghia or Titanium/X.

Thanks