Here's a link to a thread where I detailed the steps I took to install an Audere preamp in my Made In Mexico Fender Jazz. It wasn't difficult at all and it significantly improved the overall tone of the bass.
http://www.learngospelmusic.com/forums/index.php/topic,47917.0.htmlWhether you start with pickups or preamp is a matter of taste and preference, unless you can identify that the things you don't like about your current setup are a result of one or the other.
In my case, I couldn't tell whether the pickups were decent or not. By going with the Audere preamp, I am committing to passive pickups. I don't have a problem with that, since there are so many aftermarket passive pickups available, if I choose at a later date to change out the pickups, I still have a lot of options open to me. On the other hand, there are probably more aftermarket active pickup choices.
Peace,
James