TruOil is one of the easiest finishes to remove. One application of ZipStrip or any other finish remover will usually do the trick. I suspect one or all of the other suggestions would work as well.
TruOil is a soft varnish-type finish, meaning it is not very durable and scratches very easily, especially if it has been applied as a "built up" finish (on the wood rather than in the wood). That also means that is easily repaired with just a dab of it rubbed into the scratch.
The best type of finish, I've found, is a finish that is applied with a "rub in and then rub off" method. In other words, you apply it liberally, allow it to penetrate, then wipe off the excess and let it cure before the next application. About 5 or six applications with this method will give a good "in the wood" finish with a nice warm glow rather than a gaudy shiny finish.
Permalyn sealer (Laurel Mountain Forge) works great, and is available from Brownells. I just use the Permalyn sealer, not the Permalyn finish. The sealer penetrates better and faster.