So, no detail strip is ever needed, or is S&W just saying it should be done by a qualified gunsmith, not a typical end-user?
S&W is saying both. They're saying that for the normal user, a detail strip is not necessary. However, if a detail strip does become necessary, it should be done by a qualified armorer or gunsmith.
Now, the M&P is not more complicated than the 1911. The 1911 was designed so it could be detail stripped without any tools. At least, that's the theory. I would still want a punch. Teh M&P requires a punch to do a detail strip, but it's really no harder than the 1911.
I field strip my gun after a range session, but have never done a detail strip, and questioned whether I really need to spend the money to have a gunsmith do it. (And I don't want to do it myself.)
I understand that it can be intimidating. No one wants to break their gun simply because they can't put it back together. Again, it's not necessary. But if you want to do it for the experience, we can help you. If you live near me, I'll be more than happy to watch over your shoulder as you do it and guide you through the process. I've done that for bunches of guys with shotguns.
If you're not near me, I can still help. Pictures are great and I'm sure we can work through any tough part you have through this site and by taking my own gun apart and taking pictures of it.
Again, not needed, but I'm sure you can do it.