Perhaps this will save you a little time. There is a bent panel back where the fenders meet up with the frame, close to the seat. That is your inspection cover for the hydro relief valves. Open it up and use some PB Blaster on the valves if they are stuck in the up position. After they soak a little while, you can try getting a narrow stick (like a paint stir stick that you might need to trip down) in there to actuate the relief valves, the re-apply PB Blaster and work them. Hopefully, this will save you from splitting the tractor. It worked on my 125 when I got it from a swampy, mosquito infested grave, not too much different than the one you pictured.
The 125 is rumored to be the best IH cub cadet produced and quite possibly true for the NF's. It makes me glad every time I see another one saved and brought back to power. You're really going to enjoy that machine once you get it up to speed!!! Welcome to the forum and keep us posted on your progress.
Cub Cadet 123
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Still don't know what I'm doing in OHIO?.....If you find me, then please point me back toward INDIANA. 
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