Is there some sort of community that shares these cards / sentences / audio files in easy-to-import format into Anki, etc.?

Is mining your own sentences really worth it? I'm willing to bet I would agree with 80-90% of this forum's sentence picks.

I am using mnemosyne card for RTK 1 which I got from mnemosyne project website.
They are nicely done, with categories for lessons, but they are for 4rd edition, so you might need to do some edits to them