Welcome to the forum and congrats on your new machine. On the brake lever, there is a long spring that the latch arm goes through the middle of, one end of the spring hooks to the pedal shaft, the other end hooks to a tab inside the steering tower, if you remove the center plate you will see the tab. That spring keeps the latch from engaging by accident and is usually found cheap on ebay.
The pto has a feeler gauge adjustment that is shown in the regular owner's manual but you probably have to unhook the radiator and a couple other things to get to it. owner's manual also cheap on ebay.
Case is a great tractor for the lower limb disabled. If you can get up on the fender it works as a perch and you can swing/slide right onto the tractor seat. I think the later model tractors had slightly stiffer fenders that made this a little safer, below is a pic of my 1982 for comparison, i am disabled and love the fender position to get me up into the tractor.
A weak point on an old case the rear end has 5, 1/2" bolts that can work loose inside the gear case then shear off and jam the gears and even blow a chunk out of the case. This is more likely on high wheelers with wheel weights b/c of all that torque on the rear diff and weaker bolts were used in the past. There is a preventive fix for this, Ingersoll has a repair kit 5 new high strength bolts, but the rear end needs removed and opened up with the axles pulled, new seals, etc.
I am just saying this in case you find a newer machine that might fit you better, more attachments/package deal, etc, before sinking too much into yours. I think they are pretty popular in WI, good luck