while i was under there i noticed at the back of the trans there was a bunch of grime.. could this mean my trans is going out?

i know i may sound stupid explaining this but the trans looks like its in three sections.. i see the engine then the trans section where im guessing the clutch is inside then that connects to the big main section then thats connected to another section then comes the drive shaft.. its between section 2 and 3 where it looks like some kinda goo seal is leaking all the grime

also i have my pipes cut all the way up to right before they become a y-pipe(basically a really short straight pipes setup) and i noticed on the drivers side i got a ton of black grime on that little metal heat shield thing.. any one know what may cause this?

and while im driving between 1500-4500 rpms theres this hissing noise coming from underneath the center console idk if its a bent valve or my clutch is done or my trans is done

Please Help