1991 Mazda B2200 while changing gears the clutch stayed dep

Drive Train Axles Bearings problem
1991 Mazda b2200 4 cyl Two Wheel Drive Manual

I was acclerating onto highway and while I went to change gears the clutch pedal stayed on floor board. After towing I went under the truck and found the piston within the slave cylinder was no longer there. I also observed the clutch fork that the slave cylinder was connected to felt like it was free or easily able to be rocked back and forth. I then checked and found my fluid level for clutch master cylinder was empty. I purchased the slave cylinder and was wanting to know what else I should check or replace. And if the clutch fork is suppose to have those attributes of play. And what are the steps to follow in repairing the problem.