ajaisolan,
I think you mean bluing the metal parts and getting the barrel tapered. You might also be considering getting the furniture modification done. Well, none of this is going to affect the grooves.
Balance would depend upon how much metal or wood is shed off at the time of modifications and generally nothing unusual would be noticeable in this case. One fact that pleasantly surprised me was the easy point-ability and aiming once I got rid of that cheek pad on my IOF rifle.
Accuracy is more about the shooter than the firearm.
And yes, the resale value will go down after the said modifications.
best,
Rp.