Dont replace the neck unless a truss rod adjustment is not built in!!!!!
The truss rod adjustment is usually at the top of the neck under a small plate with a few screws in it to cover the adjustment. You'll probably need a long barrell socket wrench with and extension to get to it, or your best best is to go out and but a specialized truss rod wrench (cheaper). DONT REPLACE THE NECK UNTIL YOU KNOW IT CAN'T BE REMEDIED.
Jeffrey Kesler, July 2007