It appears that my water intakes are leaking under my kitchen sink. They appear to be leaking from the point where the water on/off valve is located. Is this a job that I should hire out or is it one I can fix myself? I've sweated pipes before and but I certainly don't want to get in over my head and then have to hire a plumber anyway. Is it possible that the plastic o-ring gasket washer thingys are just old and need replacing? If the on/off valve handle is stuck should I just replace the whole ting? Please advise and thanks.

Water intakes are called supply valves, supply stops or angle stops.

It depends on what you have and how old they are. 1/4 turn ball valves are suggested replacements.

Packing seals and stem washer can usually be had just taking the stem over to a "full service" hardware store. In my area, they will replace for free. You pay for parts.

You can post a pic using "go advanced".

If the handle will not turn , yes it is best to just replace the valve.

If the leak is coming from around the valve stem (the shaft that the handle is on), grasp the valve with a pair of plyers, put a wrench on the nut around the stem and tighten slightly, only about 1/8 turn.

If the leak is coming from the connection between the valve and the pipes, hold valve with plyers and tighten the nut around the pipe about 1/4 turn.