toilet shut-off valve question
Need some advice, as I'll be doing this for the first time. I just replaced our bathroom toilet and after getting it all set up and working, hooking up the supply line and turning the shut-off back on, then off again to double check for any leaks, noticed that the shut-off valve is now stuck open. The valve was soldered on and I've never done any soldering before, so I'm wondering if I can just replace the old soldered valve with a compression valve? I'm obviously going to have to cut the pipe just before the old valve. How much pipe should be left (exposed from the wall) after cutting to allow for the new valve and ring? Thanks in advance.