This. Don't change the pre unless you want a tonal change from it, and unless it has a baked in EQ curve that you want/like, most aren't worth the money.
Shielding is worthwhile, but really only copper tape, well applied. There are plenty of tutorials on YT. However, it may not make all that much difference in many rooms/venues depending in the local EMF/EMI and earthing quality. Best bet would be to change to SC J PU to a stacked or series HB version.