[quote name='neilb' post='946446' date='Sep 5 2010, 05:59 PM']If you do upgrade,keep the originals!!!![/quote]
Plus 1000!!!!!!!! You haven't actually said what's wrong with the current ones other than that somebody else has offered a general opinion on older pups. You can get really good vintage replacements by all the main brands like Seymour Duncan, Wizard etc. If you want a more modern sound, yes you can achieve that too but then is it the right bass for what you are after?
But in answer to your original question it won't be devalued if you keep the originals, assuming you are not rerouting stuff / changing the original configuration. My original 1970s P-bass is all stock. I have two late 70s basses which are not all original (one Wizard Trad and one Seymour Duncan SPB-1 as you asked). These were parts that I assembled to be complete basses so keeping the original pups was never going to be an option.