Give it a thorough going over, preferably by an experienced Europa mechanic. Do not assume anything.
Check all levels. Monitor the transaxle level until you get an idea if there is much leakage -- they all leak.
Oil the trunnions.
Check the front and rear suspension carefully and have a four wheel alignment. Insufficient rear toe can lead to some very scary trailing-throttle antics at the limit.
The S2 has small u-joints and they often don't last much more than 10K. Check them and replace them if there is any play. Use GKN, Hardy Spicer, or SKF joints. They last much longer, especially with regular greasing.
Check the half-shaft shimming! Do it now! If they are not shimmed correctly, the suspension loads go through the diff's spider gears. They don't last long.
Retorque the head and set the valves. If it is a high performance tune, then do this every 20K.
Check the coolant. Use aluminium friendly stuff such as used on modern BMWs and Volvos (blue).
The engines are very tough and sweet revving but they DO NOT LIKE TO BE OVERHEATED. Check all the hoses, etc and make sure the system is properly bled.
Use high ZDDP oils such as Mobil 1 V-Twin (20/50), Redline V-Twin 20/60 (not the 20/50!), etc.