Does the 930 run a thermostat in the crankcase as well as one in the thermostat housing behind the RHS shark-pin?
I've just removed the one from the separate thermo housing behind the shark-fin...the 964 Turbo (965) only has the one.
If this is the one you need to replace, then make sure everything's clean before you start undoing connections or removing plates, don't want ingress....I removed the whole unit, as I'm overhauling EVERYTHING (!), but I read somewhere that the only way to remove the thermostat insert cover is to drill and tap a hole in the middle (once the circlip is removed)...I did try to heat the outer casing but it wouldn't shift. I did end up drilling and tapping for an M8 hole, then using a slide hammer to gently reverse-tap the cover out. After that, the insert and spring come out very easily.
Some pics I posted in my engine rebuild thread (in the footnote):
I believe the thermostat insert and spring are the same for both the crankcase unit and the chassis mounted one.
HTH
Spencer