About 10 tears ago, I did the Park Tool School as mentioned above at a LBS. IIRC, it took about 12 hours, spread out over 3 or 4 Saturdays. The course consisted of basically dismantling the bike a piece at a time, cleaning, greasing, adjusting, truing, etc. At the end of the course, the bike basically had a complete overhaul. Some shops set them up for Jan and Feb when they’re often slow.
You’ll get to know whoever is teaching it pretty well; that could be mutually beneficial if it is the wrench at the LBS. Also, you get to see what tools you need for your bike so you can figure out what you will need if you want to do certain work on your own.
It wasn’t cheap, but worth it IMO.