Porsche 968 Info

Hi, I am currently interested in purchasing a used 968 cabriolet and am trying to do some research on it. However the internet seems to be full of a whole lot of nothing for me. i am mainly interested in a project for the winter and want to know a few things about its reliability. such as what parts are common to have break and what they usually end up costing? as well did all 968's have a 4 valve head? what are the differences between the turbo engine and the non turbo? (aside from one having a turbo of course! were there any differences in the actual engine?)

If anyone knows any of this or could point me to a good resource it would be much appreciated!