Lenses for K 30

I bought a K 30 with the DA 18-55 WR lens last Monday.  I am really enjoying the camera but lots to learn for sure. I know that it won't be long before I am going to want a longer lens and an external flash, so I am looking for some advice/input.

1) In a lens I would like a zoom up to around 300 mm (old 35 mm numbers). I am wondering if anyone besides Pentax makes water resistant lenses and even if they don't what other lens manufacturers you folks might be using.

2) I am thinking that in a  flash specs comparable to the Pentax 360 flash is likely what I need minimum.

As a bit of background, I do a lot of nature photography and sports photography and the later includes indoor action shots of my grand daughters ice skating, playing volley ball, soccer and horseback riding.

Now if I had lots of money probably would be easy as I would buy all DA* lenses and forget about it (but then if I had that kind of money I probably would have bought the best DSLR body Pentax has) but I am retired so need to stretch my "recreational" cash a bit.

Thanks in advance for your help. And of course any helpful hints on the more subtle things about the K 30 will also be appreciated.

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Bob Corson