P J pot replacement

[Dr.Dave]

Hiya folks - just to kick off by saying I'm no sparky beyond wiring a plug or soldering a jack so please keep that in mind.

 

Just picked up a P J which I'm modding and one thing I want to do is dump the two vol control ( as per jazz bass) set up. I'd like to replace the second vol with a pup swing pot.  It's need to have a click in the mid position ( are they all like that ?? I don't know ).  

 

So - I'm going to need a suitable pot. Any idea which one I should get ? I read online either a 250k or 500k should do it but I don't know the difference. I'll also need a wiring diagram which I can most likely follow.

 

All thoughts gratefully accepted.