904 Leaking. What to check first?

To me, it looks like it's time to get dirty. Get the car up on stands, get some good rubber gloves, some eye protection, some Gunk degreaser & brake clean. Clean all of the heavy grease & grime with the degreaser & a brush. Wipe it all down & clean the light stuff left with brake clean & a brush. Replace the cheesy rubber hose & clamps with a couple of compression fittings & a short length of the correct tubing. As stated, take a look at the shift shaft seal & replace if needed, along with the o ring for the NSS. Top off the fluid, drive it a bit before putting it back on stands to inspect & fix any other leaks.