I can certainly understand a firearm owner wanting to be able to better diagnose a potential problem. That, and being able to actually make any necessary repairs and corrections, was at the heart of my desire to become a LE armorer.
I'd had some bad experiences of my own with a few commercial gunsmiths ... and "feeling comfortable" trying to "do something", myself.
I envied our agency armorer his abilities, skills and experience. I was naturally anxious to be able "fix things" myself on my own guns, without having to wait for him to get around to it, or having to return one of guns to the factory.
It was also why I worked to expand my armorer training to cover an assortment of different makes/models of firearms over the years. And accumulated my own set of tools needed for a range of firearms (since I realized the day would arrive when I would no longer be able to use the agency armory tools). I wanted to be able to do as much of the simple service, maintenance and repair of my own guns as possible, including after I retired and moved away.
The thing is that properly diagnosing a suspected problem (or problems) is usually the hardest part. Not recognizing and identifying the actual problem(s) is where things can really start to become frustrating, and create the opportunity for things to really
Trying to pry/lift off the side plate can create the potential for damage that may not presently exist. Side plates are expensive, factory-fitted (and polished with the frame) parts.
Ditto mixing up the side plate screws. Or cranking down too hard and stripping the threads, snapping off the screw head or cross-threading them.
Also, once the side plate has been removed, not everyone may be able to properly re-position the hammer block (external hammer models) so it functions normally and isn't damaged.
Rather than risk adding to whatever condition(s) may exist, why not simply have a licensed local gunsmith open the revolver to give it a cursory inspection? If it's just accumulated fouling, it would be an easy correction. If it appears to involve something else? Then the owner can contact S&W to see what they think (and also presuming he bought the revolver new, after the company had started offering their limited lifetime warranty to original owners).
Depending on the owner's level of experience and mechanical abilities, and the inclination of the gunsmith, perhaps the gunsmith might be willing to take a couple minutes and demonstrate how to properly remove the side plate? Of course, this creates the potential for someone not being able to resist frequently opening the frame.
As far as someone "feeling comfortable" disassembling a revolver, after never having done so before or having received at least some basic instruction?
Well, after having been to more than 20 armorer classes, I've seen at least my fair share of new armorers, working on factory-provided guns, feel perfectly comfortable learning how to work on the guns ... right up until the moment they lose parts, damage something either removing it or re-installing it, damage the serial-numbered part of the gun
(the expensive part), etc.
I've occasionally offered a few of our folks some instruction on properly removing the cylinder & yoke of their personally-owned revolvers, so they might lightly clean and lubricate the 2 yoke barrel bearing surfaces. These are folks who I've known for some years, generally being shooting enthusiasts who are revolver owners, and who used to carry issued revolvers. I have a grasp of their level of mechanical abilities. Most everyone else usually realizes they're better off limiting themselves to basic user-level cleaning practices.
Of course, revolver owners being curious about "how their guns work", and "feeling comfortable" learning how to disassemble them, or making some minor "improvements", "doing trigger jobs" or wanting to start changing spring rates, etc?
Well, those folks often seem to help keep gunsmiths and factory repair technicians/gunsmiths remain employed.