To depressurize the system, turn the engine off. Then lower the arms and bucket, wiggle the joystick to all positions until any movement stops. Be ready to catch any drips as the hoses drain when you disconnect them. Take pictures and mark hose ends, because crossing a couple can bedevil you.
I doubt replacements are available from Kubota. But you can have them made at a local shop by taking one in and letting them duplicate it, or order them on-line by measuring them and specifying the end connection.
Discount Hydraulic Hose and other on-line vendors have references for how to measure and specify the ends. Yours are probably JIC, which is a 37° flare. Be sure to check both ends, most of mine were straightforward, but a few had smaller connections on one end. I ordered the 100R16 hose.