I have limited plumbing knowledge so pardon the question if foolish. I have a leak under a bathroom sink that has double shut-off valves (h&c). On the hot side the leak seems to be a drip from the shut-off valve handle. The shut-off valves attach to grey plastic supply lines and are secured by what looks like a copper ring. On this hot side the copper ring appears slightly corroded as well. The cold side looks as though the angle stop was replaced at some point -- it looks newer and that copper ring looks to be in good shape. The house is about 12 years old but we've only been here for 2.5 years so I do not know a lot about the history.

And if I should just replace this angle stop, is this a fairly straightforward process?

Thanks in advance!

Nobody is born knowing this stuff. I am not a plumber, but I have picked up stuff over time. It it is just dripping a little around the handle, just tighten up the nut a little. Usually that fixes the problem

If you do have to replace it, the copper ring sounds like a crimped PEX joint. No redoing it without a crimping tool. I would buy a threaded ball valve and a flexible supply tube. You might need an adapter too. Look around at home center or a hardware. You will need to unscrew the tubing from the faucet. Post back for more details after studying things. Ball valves almost never leak around the handle and don't let water through when closed.

"And if I should just replace this angle stop, is this a fairly straightforward process?"

No need for replacement. Open up the angle stop a half turn when the water starts to leak past the stem take a pair of pliers and snug up the big bonnet packing nut until the leak stops. Good luck, Tom

Thanks so much! I did tighten up that nut just behind the handle and that did it. Thanks for saving me a lot of trouble!