great stuff AYIA
I'd love to hear more form you on lenses. Can you share more recommendations?
First thing to do is check out the Pentax lens compatibility chart over at
http://www.mosphotos.com/PentaxLensCompatibility.html
ALMOST all lenses are usable, but a few aren't or work with limited metering. But an example would be a used Pentax SMCP-FA 50mm f/1.4 runs about $300 where a digital specific 55mm f/1.4 is about $640. The 50 is great for shots of the kids(both are really) or head and shoulder portraits, but the price difference leaves you enough money for a second lens. The Sigma 28mm f/1.8 EX Aspherical Macro would be great for landscapes at around $340. Right there you have 2 lenses for the price of 1 that cover a large portion of uses. Both are also very sharp, the advantage of primes.
For a hundred more than the kit lens(18-55 f/3.5-5.6) you can get a Sigma 18-50 HSM(hyper sonic focus motor) f/2.8-4.5.
I generally carry a Sigma 17-50 f/2.8, 50-150 f/2.8 and a 10mm f/2.8 fisheye. You really don't need constant 2.8 however if you're not shooting in low light all the time.
I am using the K-7 for serious winter mountaineering, fly fishing, family, etc.
Winter mountaineering you have plenty of light, usually very harsh light light reflecting from snow and ice, so polarizing filters for the lenses would be recommended. For the outdoor stuff find a lens that doesn't go over f/4.5 at its longest zoom and don't worry about high ISO because you'll most likely be shooting in day light. A TTL cord for your flash will allow you to move it around to light those darker shots around the camp fire.
all the best and highly looking forward to more of your expertise
As I've said elsewhere I'm no expert just a guy who got lucky enough to spend his weekends taking pictures of hot woman getting drunk:wings:. My best advice is to not worry about buying a ton of lenses right away, even inexpensive manual lenses, and buy the body alone to save $120. Put that towards a Sigma 18-50 f/2.8-4.5. The glass is better, the focus is quicker and the price is hard to beat if you're already willing to drop almost 9 bills on a camera. It doesn't have the zoom of a 70-200 or even the 50-150/50-135 but it is a great all around lens. Besides you have two perfectly cheap zooms attached at your hips. Just walk a little closer.
By the way, the camera is environmentally sealed but the lenses and mount are not. There are sealed lenses(mostly primes from Pentax's DA* line) but the price does jump quite a bit.