engine sound from "vvvvv" to "thththththth"
 

I AM FAR FROM MECHANICAL. Haven't even removed covers to see my engine yet.

But, got new plugs put in months ago... could one be bad or a wire come lose, and can I actually check it myself?

I'm pretty sure the engine used to have a smoother "VVVVVV" sound, and now it kinda sounds like a piston is missing or weak, "ththththththth" (tongue bouncing around in mouth).
Still kinda smooth and seems to drive fine.... MAYBE less power? hard to tell.

Ideas, for a not mechanic type with an open Saturday to poke around?

No, I don't have one of these plugin diagnoser things yet

Since you recently got the plugs replaced, by the change of sound you are hearing it could be a loose spark plug, but since you don't know what you are looking for (sorry...), you should take it back to the person that replaced the plugs and re tight them.
Good luck!