how easy is it to change out pickups? and what would be a better one to get?
Changing pickups out is real easy. Just unscrew the old ones, snip the wires, and put the new ones in their places. I'm no expert on pickups, I've got some seymour duncans in mine, but a search for "p-bass pickups" should help you out.
You don't necessarily have to change out the pickups. I have an SX P copy, and I'll put that pickup up against any pickup on the market. The problem I had was with the fretwork. I had to give it a fret dressing before I could use it without it driving me insane. But now that I did that, it plays great and sounds just like a Precision. I've been using it as my main electric on gigs for a few months now playing with Bowzer from Sha Na Na. Not a word of complaint from anyone
Mexican-made Fenders. I bought a used Jazz a few years ago, put new pickups in it, and it sounds great. This might be a little higher up the food chain than you were thinking, but they aren't that expensive if you buy them used, and I think they are pretty well made.
I bought an SX JB57 b-stock. $84 dollars to my door (small chip in the finish on the fret board, non-issue in terms of play-ability). I had it set-up and was going to swap out the bridge, but you know, the stock one wasn't too bad. I think the P/Us are fine as well. I put some flat wounds on it and it really does sound like a j-bass, honestly. My other bass is an G&L L2000 (US) and they're completely different beasts, which is why I took the gamble on the SX.
The neck on the bass is kind of ugly. The finish on the head stock is a weird orange-ish color. It's a sunburst body, but the pick guard is white. I'm going to change it, but that's a bit of a pain as stock Fender replacements don't fit the SXx.
A friend bought a cheap Squire jazz and I'd say his is, maybe, just maybe, a tad nicer than the SX, mostly due to the what I prefer as a satin finish on the back of the neck (but some steel wool ought to fix that on the SX). His was $180 I think.
pick up a used MIM P-bass or J-bass off of Craigslist.. I think I paid $200 for a P-bass... swap out the pickups if you don't like them, but the bass will play and sound just fine (a few good records have been made with P-basses, I think)
Squire Affinity P-Bass, about $180. I've been playing bass since 1968, helped my brother select a beginner's bass for his son several years ago and liked these so much, I bought one for myself. I dropped a Bartollini '64 P pickup in it and had the nut filed to accomodate the lowest strings of a 5 string set, so it's a 4 string /5 string. The neck profile's really nice, and the intonation was dead nuts on right out of the box.
Yet another happy SX P-bass owner. The thing cost $110 and is absolutely usable. The maple neck actually has some flame to it and the finish is like glass. The body isn't quite as thick as a Fender but otherwise it's all there. I personally like the pickups a lot but others might find them a bit twangy.
Purely for the sake of having bass to record with I'm reasonably happy with this dirt cheap Dean I picked up, I think for $80. This bass would be no use for gigging with given the pickup and shoddy electronics (no big deal to fix), given the lo-fi nature of the beast it's actually not bad at all with a decent tonal range, slap suffers on it, but that's about it, and I had to spend a little time with a screwdriver when I first got it fixing the dodgy jack input. The pickup would probably be ok if you dipped it too.
I would say though that for only $150 more you can get a bass that would actually be worth having, the only reason I got this was because I knew exactly what I wanted, i.e. the cheapest possible bass, and I know how to get the sounds I want from it even if it is cheap.
I'm no bass player...but I needed one...I picked up a Yamaha for about $149.00. Very good for the money. I use DI and amplitube so I can pretty much dial in any kind of sound I want. Anyway....I have found most of Yamaha's low end instruments are quite good for the money