Without seeing the wheel I would guess that the rim needs to be "adjusted" with 2 blocks of wood and a rubber mallet, then trued radially and laterally. If the rim has a flat spot it will need to be rounded out before truing, otherwise truing will result in uneven tension and future problems. Check for cracks in the rim around the spoke holes before spending any money on the wheel. If you don't have any cracks it is probably worth repairing.
Al