Re: pimp my squire
Will it make that a much better guitar? Yes. Without question.
Will it make that guitar as good as the guitar you could afford by selling it, and buying a complete guitar of higher spec with that money+the upgrade money? Probably not.
Your upgrade options at the low end will generally much improve any instrument, but ultimately, you're an end user with no economy of scale. You're not buying bridges, tuners, or electronics in bulk, and you're two steps further down the chain of distribution, which means two steps of markup on the price.
A manufacturer can afford to bypass all of that, and for that reason, upgrading low end guitars is generally just nowhere near as good in the long run, as buying a better guitar in the first place.
As for what you're upgrading to and why... have you considered what you want to achieve with these upgrades? Its very easy, if you don't have experience, to think of upgrades as "Better" rather than "different".
Ultimately, that Nocaster pickup set will sound markedly different to what you have already. You may OR MAY NOT like the change.
For example, vintage voiced pickups tend to be bright, chimey, but not have much output. They're not, in most peoples eyes, super great for getting a metal tone. Even a cheapy high output set, might do much better in that regard, because they'll have at least been designed for that.
Can you give us more info about this? Ideally I'd like to know:
1 - What about this guitar do you really like?
2 - What about this guitar do you really HATE?
3 - What kind of music do you play?
4 - How long have you been playing?
5 - Who are your favorite players and what do they tend to use?
If we can get that written down, I'll have a much better idea of what kind of upgrades will really get you closer to what you're looking for.