I purchased several of the "technical manual and armorer's course" and found them useful. They show how to disassemble, clean and re-assemble the guns. They also show some of tricks needed avoid mistakes and how to check the gun for proper function. Some of the presenters are well organized and some less so. Some things surprised me, like putting gun parts in a steel vise (I would have put the soft jaws on first). One odd thing is that a couple DVDs did not run properly and required a cleaning to work well. I have not seen any of the gunsmithing DVDs so far.
You might take a look on ebay for some bargains.
You might take a look on ebay for some bargains.