the biggest difference I've noticed is that CTS pots tend to last quite a bit longer without getting all scratchy as cheaper components tend to do. the original pots in my '72 EB-3 are still going strong, whereas I had to rewire my '95 Rivoli due to excessive noise. the cheapies were ok as long as they were kept in one position but as soon as they got turned, it was scratch city.
for caps, I don't really know. I have basses without Orange Drops and they sound good to me. caps aren't very expensive and the Orange Drops have a good reputation, so that's what I buy. since none of these components are expensive, I tend to lean towards the conventional wisdom. I should add that I'm strictly an amateur. any knowledge I seem to possess comes from trial and error experiments and from what I read on the net and in various magazines.
regarding pickguards, there's a bunch of places on the net that will make one for you, using the original as a template if they don't have a template already. I got a new guard for my Ripper from Jeannie's and it was a pretty close fit (some of the screw holes weren't quite exact). other folks have been very happy with their work, but I'm not sure if I would use them again.