Thermostat's not too tricky to change, just remove the plastic that holds above it and you'll have easy access to it.
Also I'd recommend you to use a strong zip tie on the exhaust rubber mounts because those fail so often. I've gone through three rubber mounts on each 3 rubber mount locations.
You might see an oil leak just above the plug of the maf sensor, that'll be probably a rocker cover gasket failing.
The cig lighter also doesn't fit most of the normal plugs, you can change this out for another modern one.
You may get an earth wire issue and that'll stem from one of the rear lights wires being burnt out. You can fix and brush away at the connection/terminal, which I did so many times, but eventually just swapped the plug out by cutting the wires and no issues since then.
Genuinely a nice car. I don't have the 16v but the 8v, so a little slower. I've had the seats changed out for the alpha romeo cream ones, had both back and front but the back are quite uncomfortable and ended up getting rid of them but the front are comfortable.
I use it mostly as a backup car now and looked after it pretty well for the last 4-5 years of owning it and was the first car I ever did any extreme mechanical changes on it. Best and simple car I've owned.