If you have just a banjo joint leaking, just fix that, yes i would do a power steering drain, otherwise your seals will swell up, there was a post on 156 power steering fluid change, about 3 months ago, quite a worthwhile and straight forward job, $15 for a thermostat?, no these days the thermostat is part of the housing, and is not replaceable on its own, try $90-$160, depending on Genuine \ Non Genuine \ temperature gauge installed \ not installed, quite a straight forward job, remove flexiable duct on air cleaner assembly for better access, and the original Alfa hose clamps have to be 'mongrelled' off, just replace with good stainless steel tridon clamps from Repco best to use the RED coolant, i use Nulon long life that has anti fungal growth in it for long life, i have used the 'blue' coolant in the 33, if i remember it was LOCTITE brand, don't use Nulon 'green' coolant, i did and it rusted up, but the Nulon 'green' is recomended for motorsport applications, as it contains no Glycol, which makes race tracks nice and slippery, when it leaks out, Parafin is what the English call Kerosene, the make of coolant as recomended by Alfa Romeo is PARAFLU, according to the sticker on my coolant tank, it can be obtained in Australia from Alfa Romeo dealers, after market Alfa spare parts places and the U.K. at places like E.B. spares, but freight is quite expensive due to the restrictions on fluid transfer laws, Colin.