John Deere 310D Reverser Hose problem

Hello all. I have recently become a weekend farmer and I am borrowing my father-in-laws backhoe. It is a JD 310D 1996(?) with engine serial number T04039D549150. Not sure how many hours are on it. The machine was working fine when I parked it. The next week I started it and let it idle for a few minutes and then backed it out of my barn and stopped to talk to my wife a few minutes. When I started to back up some more it wouldn't move. It felt like it wanted to but did not go back or fwd but the buckets all worked. When I got down to look I noticed hydraulic fluid running out of a hole in the side of the frame where the batter compartment is. I checked the fluids and the reverser oil was empty. I had to leave it for a couple weeks, and as I dug around and tried to find where the fluid was coming from, I found a hose coming from the reverser to the reverser dipstick tube that had come apart. I replaced that hose and I cleaned the mud out of the holes in the bottom of the frame where the fluid was running out of, to see if I could see anything else but couldn't tell anything. After putting a couple gallons into the reverser, and letting it run a little to make sure I got the proper amount, the fluid started running out of the holes the bottom of the frame again. So, there are three hoses running from the oil cooler into the frame and out the back. One of those has ruptured but I'm not sure which one because they are encased by the frame. One goes to the reverser return port, the second goes to the rear transmission case and the third goes to the hydraulic oil filter. Can anyone tell me if the second one or the third one would be using fluid from the reverser reservoir? Also, if I replace one of those hoses and take off the reverser oil pan and clean the suction filter screen, how much fluid will I need to fill it back up again? And, is there any other maintenance that would be recommended while I'm at it? I'm a couple hours into the mountains so I wanna try and take what I need to get 'er done or I'll have to wait another week to get back up there. Thanks for any help.

John Deere 310D Reverser Hose problem