Hello AA and welcome. My Spider is an early model with manual roof too, you should have loads of fun. Apart from the basic mechanics which you are already familiar with, the main things to look out for are suspension, arms and bushes, all aspects of which are well covered on this forum. Other things are just characteristic quirks, such as bonnet struts don't last long, fuel release cap can sometimes stick open. The fuel release and internal boot release will only 'fire' if car is turned off.
The electric aerial for the stereo can sometimes fail or just stay in the up position. No real corrosion worries, front end is all plastic anyway !!!! Have fun.