1) I've always removed the brown cowling around the control levers to pull that floor plate - why exactly, I can't say atm as I don't have a 580SK in front of me, but there must be a reason...
2) Your plan to lift the machine off the transaxle using machine hydraulics - on a 580SK, after you drain the oil to remove the oil suction hoses - you should NOT run the engine as the charge pump will be running without oil supply & you will destroy it.
If this is the only option you have to remove the transaxle - you will need to also pull the torque converter housing (inc charge pump) before running the engine.... creating a little more work.
3) Pulling the wheels is no big deal. They are always the first part I remove. Using the stabilizers, positon the machine so the wheels are just touching the ground, remove all the wheel nuts, & simply walk/rock the wheels toward you & away from the mudguards - no lifting is required, but balancing skills, yes!
4) These machines have no brake slave cylinders, I'm guessing you meant
master cylinders. The worst part of this design is that they are retained with bolts & nuts - so it's easiest with two people - one in the cab & the other under the hood. I have had to do this many times on my own, things you learn how to do as neccessity....
** TIP - a pair of extra long reach long nose pliers are useful in removing the pushrod clevis split pins.
The master cylinders do not pit & rust, as do most automotive types using brake fluid - another advantage of using mineral oil - they usually have a fair bit of black sludge in them (dirt) & clean up well.
The one that is tight, if it is because of swollen seals - it may have some scoring inside it - which may hone out - something you will decide when you get to see it.
