I found the donor guitar on Reverb... cheap. The neck has a wicked back-bow. That’s why the new neck.
About the Sticker on your headstock. It will keep you from selling it and regretting it later
Had they had that color when I bought mine and didn't have the whammy bar mine had, I might still have it even with 3 pickups. Yep the stock pickups were crap. I got some Reverend P-90's and put in it at the time. About their necks they were never very sturdy. Wouldn't hold a tuning on the SX Bass I bought years ago.