The Glock 30 is one of the most desirable models, because there's not another subcompact plastic fantastic .45 quite like it. It's actually pretty popular and not obsolete at all.
I don't quite understand your concern. If you just need magazines, they're available all over the place. Like
here.
I've never seen a gunstore that didn't carry them either.
I'm also not sure what the magazine seller was trying to tell you.
There are drop free magazines, non drop free magazines, LE/Mil marked magazines for various Glock models. For some people in certain locales, certain magazines have to be avoided (such as the LE marked ones). Could
they have been speaking to this?
Or were they speaking to the fact that there are first, second, and third generation Glocks? I don't think the Glock 30 ever had a first generation style frame and in fact I'm not sure I've ever seen one without the rail and finger grooves characteristic of a third generation frame. But I'm not a big Glock guy so I wouldn't know. But it doesn't matter, any new (factory) magazine you get should work great, unless there's something about this particular model I don't know. I have a second generation Glock 19 and I used magazines made in 2006 all the time without difficulty.
If you like the Glock 30 rest easy, it's a very popular product and its accessories are easily had everywhere. If you are thinking about a 21, remember that Glock 21 magazines will work in the Glock 30, they'll just protrude.
As far as what you should do, if you like your Glock 30 buy six magazines and a decent holster for it, shoot it, and clean it as necessary, and enjoy.