Hi there JB,
I have never resealed a floor jack. But I have resealed a lot of hyd cylinders. Sounds like you should have the correct seals. I googled resealing a walker floor jack and found a few you tube posts, you could look at those for starters. It is a good idea to do a good job of draining the cylinder first. Get the end you will be taking apart as clean as you can. It will be messy, even well drained you could have a bit of oil coming out with the rod and packing, so prepare for that. Pay close attention to the seal lips, rod dirt seal lip towards the outside, oil seal lip toward the oil.If there are backing rings behind the seal pay close attention to how those are arranged. A Walker should be a good unit designed to be rebuilt, so you have that going for you.
Good for you for giving this a try, and best of luck.
B