Thought I'd give a little update on the status of the bass.
I still stand by my prognosis of the bass' problem. I took it into the Long and McQuade where I got my wenge neck. They seemed pretty "oh, cool" about the bass and nothing more, and I told them the story and what I think was wrong with it.
The dude said that Warwick are notorious pains in the asses when it comes to getting stuff. They can get a wiring diagram, but they will NOT give schematics. Crap, some stuff comes with the schematic in the bloody instruction manual! Parts take around three months to get from them, too. So basically, if the problem is what I think it is, the repair won't be a problem at all. Anything else requires a full preamp replacement. If that's the case, chances are I'll go third-party. I don't think I'll have to, though.
The downside is that right now they say they have a four week turnaround - so I probably won't be able to have it for the show if that's the case. However, my friend reckons it isn't - they said it would take the same amount of time to get his BC Rich guitar fitted with new pickups (one of the good BCs, a NT Mockingbird in the same colour scheme and top configuration as mine) but it only took them a week. This was Tuesday. So we'll see!
I hope the chronicle stops at three so I can resume the Gospel