Its hard to convey "how hard is it to do PLC stuff" in English language. Kind of like trying to explain sex to a virgin. You just have to do it. All the different platforms have different little idiosyncrasies but they are all based on the same principle, relay ladder logic. learn that (which is so easy it's almost boring) and then it's just a small learning curve (how to set up backplane, address I/O, create timers, search, crossref, compare, how to not download, etc.) with each different platform, no different than when you have to learn a new version of windows (well actually a little harder than that, but you get the picture).
Then there's higher level PLC stuff that deviates from the traditional ladder stuff, text based writing of code & whatnot where some programming experience is helpful, but even then it's not so hard as to be unlearnable.
If you've got the time and the money to take the training, take it. But remember, a lot of companies will pay for this type of training, especially if they have lots of different types of PLCs they can't expect you to know everything.
The plant I work in didn't send me to any training, but they also don't stand over my shoulder while I'm trying to figure it out, saying "are you done yet, are you done yet?".