speaking from S2N experience its very simple.
1. 5 Star European Breakdown Cover.
2. Make sure everything is good before you go.
So if you know the alternator isn't happy sort it before you go. Make sure the car has excelent cooling as thats a big killer, for instance check your hoses and so forth.
Make sure you aren't leaking/burning oil. And put new oil in a couple of weeks before you leave. Don't drive with manky old oil and try and match what comes out with what goes in as engines, especially older engines like the same type of oil, even if the manual gives something totally different.
If you are leaking - the cost of your trip will be huge, plus the leak can get bigger and then you are screwed. If you are burning, then, choose another car. All sorts of things can go wrong if you are burning.
Generally the cars that didn't make it to Naples on S2N had known problems before they left the UK or engines that made such bad sounds - you wouldn't go to the shop let alone southern Italy in them.
Even if the big ends go - its not that bad. Just shove in the thickest oil you can find, and drive home carefully, never going above 3k. A Toyota had knackered bearings on the first day, still drove 2800 miles. The car killed itself as the owner drove it back up his drive after S2N.
And make sure your exhaust is good.
After that - you should be okay to go. Just take it a bit easy as its an old car and deserves respect.
Have fun.
Tin
added - whatever you do - do not let the car overheat. if it gets hot, take it easy or rest it. if the car overheats then you put extra pressure on the cooling system and something else may break. if it does overheat, rather than sit by the road like a lemon waiting for it to be cool enough to touch, pour cold water across the top of the radiator, this will cool it a lot faster.
