Thanks for the input everyone, much appreciated. And thanks Back2Alfa for the boost.
I have been able to fix most of the initial upsets, including a thermostat change which resulted in the temperature now stabilizing at 90 C. Also replaced the clutch, but this did not fix the gear lever moving around. Doesn't really matter that much to me though.
However, there are still a few quirks I've been wondering about.
Firstly - the fuel gauge is very unreliable. If I have 5-15 liters in the tank, the fuel gauge shows anything from completely empty to 25% full. It varies every time I turn the ignition on! Could this be battery related?
The engine runs fine, so I can't imagine it being the MAF, as has been the case in some of the threads here.
If it is the actual gauge, would changing it be a complicated procedure? I can't even seem to be find the actual spare part anywhere, despite searching for fuel gauge/fuel sensor etc.
Also, the brightness of the dash lights is very low, even when the dimmer is on max. I can hardly see the odometer reading etc. in normal daylight. This was not the case with my last GT. Anyone know if there is an inexpensive way to fix this? Or does the dimmer switch only affect the actual "redness" of the km/h and rpm gauges etc and not the odometer display? It doesn't seem to make much difference how high/low I set the dimmer switch.