I'd just replace them with "Shark-Bite" 1/4-turn, 1/2" PEX x 3/8" compression angled shut-off valves - like you'd use under a sink. Shut off the water source.
Looks like there's not much slack in the lines that feed the valves, so you'll probably have to remove the clamps from the lines. Once you've removed the feeder lines from the valves, pull the valves up a little so you can cut off the drain lines and let them fall through the trailer floor. Next, attach a standard 3/8" compression x 1/2" FPT x 12" long vinyl
sink water line to each new shut-off valve. Cut off the 1/2" FPT fitting and discard it. Then push the cut end of the faucet line through the hole in the floor for each line. Push the "Shark-Bite" shut-off valves onto the PEX feeder lines. Fill the gap between the sides of the floor holes and the vinyl sink lines with a little "Great Stuff" or caulk and your done! EASY PEASY!