1st manual Car. Couldn't get a better version due to money wise. I don't make that much. So fixing some stuff and tuning the truck has been an issue. I got it for cheap and I'm learning everything about it as I go. I believe this is W56 transmission there's a plug that's connected that's leaking fluid. Is it the transmission fluid? It seems black. I ordered a fill plug and drain plug with washers. Just incase if it's done for so I can just replace it when I drain it. But if anybody has any idea what should I do with that plug on the left that's covered in oil. Every help is appreciated. Whatever worked. This is gonna be my daily driver. It is right now . Let me absorb all of yous knowledge. Thank you again

 

That appears to be the back up light switch. Tunes on the backing up lights when you put the transmission in reverse. Easy to replace and it should have a crush washed under it that seals it off.