2 weeks of sitting with two different doses of penetrating oil and the truss nut is still stuck. I don't want to put much more oil on there because of the concern of the oil soaking into the wood. Is it time to take this to a luthier?
May be worth it to take it to a luthier. I have removed one by cutting it length-wise with a modified piece of hacksaw blade. It took a good while to do since you are basically scraping a slot through the brass. At least the brass is relatively soft. The teeth cut best on the pull stroke so have them angled toward you and use mild to moderate pressure. Modified with a bench grinder.