My main water shutoff valve is developing a slow leak. It looks like the leak is coming from the packing nut. I’m a little hesitant to tighten it a quarter turn because i don’t want a slow leak to turn into a steady stream. The house is about 60 years old so I’m also wondering if maybe the valve itself just needs to be replaced, it looks like it’s seen better days. Would me trying to tighten the nut on the gate valve a quarter turn fix this? Or is it best to call a professional plumber? Any tips or advice would be much appreciated. Thanks!