reading all the other threads you made, it would sound silly to upgrade AND the whole tremolo system AND high end pickups on a $200 to $300 guitar...
save up the money and buy a whole new (or 2nd hand) guitar in a higher segment
(that way, you'll have the other one still, it will come in handy when the other one is in for repair, setup or anything else)
besides that, pitfalls in second hand pickups it that the cut of wire isn't long enough or the fact that it is easy to scam and to sell a fake pickup
