How difficult is it to remove a bathroom sink cabinet unit and hook up a new one?”
First, you should have shut offs on your water pipes under the sink. Remember lefty loosey and rightey tightey and close them. Then you can unhook the supply lines. If you don’t have shut offs already in place, then you will have to turn off the water while you tear out the cabinet. Second, put a bucket under your P trap (probably what you called your J joint) to catch any water, and go ahead and unhook the sink from the drain line. Now you’re ready to tear out the cabinet. You can either take the sink and faucets off separately, which you might want to do if you have any thoughts of reusing any of them, or you can just take it out as a unit, removing any screws or anything else you see holding it. I usually like to take the entire counter top, sink and all out as a unit, and then the base cabinet. I think that waworks best. If you didn’t have shut offs, you have to cut your supply pipes while the water is off and you should install shut offs before you go further. While the cabinet is
Your trickiness comes in these places: Disconecting the water lines. Of course, it depends on what kind of lines you have, but if you have hard copper, it’s very, very east to twist the lines when removing old hardware. You don’t want to do that, because it is plumber time! Hold the copper side very lightly – I use a channel lock with cloth to hold the copper while I loosen the water pipes. Getting the old and new drain lined up – that can be a problem. Measure, measure, measure and connecting the cabinet to the wall – make sure you find studs.
