[quote name='gary mac' post='1268227' date='Jun 14 2011, 09:00 AM']I would do it. Not as a money maker but just for the pleasure of improving an already decent instrument.
I've just completed a Squier P bass upgrade and really enjoyed doing it. To me it was absolutely worth doing and has made what was a playable but dull instrument in to something very pleasing to play and a pleasure to look at.[/quote]
That's my view too. I'm about to embark on that route with my Squier Affinity P. As it stands it is a nice player, and surely that's the main thing. I've heard of people who have tried to go to the "top of the mountain" and bought "real" Fenders, only to be disappointed with the playability, quality control, tone, etc. So if you already have a bass that pleases you but it can be improved - go for it!
I think the neck is probably the crux of the matter. Once you start thinking of replacing the neck, you are basically saying that you don't like that bass. Pickups and hardware fine. Nut, bridge, tuners definitely!
You will never get the money back, so do it because you want to do it - not to make a profit as the total will never be worth the sum of the parts. At the end of the process it will still be a Squier!