555 deere fluid question

Let me start off by saying im very new to the heavy equipment world this forum has been so much help thank you in advance. OK I have an early 555 and would like to k ow if there is a difference between the hydrolic fluid and transmission fluid. Where do I fill the transmission fluid? I found a dipstick on right side of the engine bay, that is as your sitting on the machine, and it was bone dry figure it was tranny dipstick then again I spent 4 hours looking around under and above and cant find the oil dip stick or where to add the oil for that matter. one other question there are two rubber plugs at my feet while in the seat on top of tranny housing one of them is partially gone and I fear rain water may have gotten I

in is there a way I can check this. The machine has been sitting for around 6 years being last started 2 years ago for about 30 min. Sorry for multiple questions in one post but im so anxious that I now have time to work on her

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