I have a carbide router bit that is in need of sharpening. Can it be saved or do I need to buy a new bit?
As long as the bit is not excessively dull or nicked you can sharpen it yourself. Excessive wear or damage to the bit's carbide cutters will require professional servicing. Professional sharpening usually costs less than $10 depending on the bit.
Before sharpening check to make sure the bit is actually dull and not just in need of a cleaning. Cleaning the pitch and resin off your bit may solve the problem and it's the first step in the sharpening process. You can clean the bit with a solvent like WD-40, paint thinner, or denatured alcohol.
To test the bit's sharpness, carefully scrape the cutting edge gently across your fingernail (Caution!). The blade is sharp if it scrapes off a little surface of the nail.
If the bit is in need of sharpening you will need a diamond paddle honing stone and water. Four to six passes of the carbide cutter (not the body of the bit) should be enough. A 600 grit paddle is all that is needed for a light touch up. More aggressive sharpening jobs will require a preliminary sharpening with a 325 grit paddle followed by 600 grit.