Fantastic camera! You'll have a great time with it.
I don't have any experience with them, but there is a
Magic Lantern guide for the K10D as well as a a couple of tutorial DVDs (
1 and
2.) I would guess that the book is the best bet, I've heard pretty good things about the Magic Lantern guides, and it's not terribly expensive.
I too went from a K1000 to a Pentax DSLR, so I can understand what the transition is like. First off - unlike with the K1000, you probably won't be shooting in Manual mode very often - in fact, very, very rarely most likely. For everyday shooting, Program mode will basically do nearly everything for you. Av lets you manually control the aperture and Tv lets you manually control the shutter - those three modes will do everything they can to automatically keep the exposure correct. In Manual mode, exposure is 100% up to you. You can hit the Green button to set everything to recommended settings then modify if you like.
Ultimately, I would recommend leaving it in "P" mode for a little while and get the feel of the camera. If you find yourself in a low-light situation and are getting blurs, try setting the ISO higher (it probably defaults to 100-800, similar to the K100D, so try 1600); this will give slightly higher levels of noise but allow a faster shutter.
Once you get comfortable with that, you can start to play with Av and Tv modes. But you can leave full manual mode to the K1000.
YEKCIM said:
I believe I am correct in saying that the K10D does very little in-camera processing, at the default camera settings, meaning that you will need to obtain and lean to use some sort of editing program such as PhotoShop, Lightroom, Paint Shop Pro, or even Picasa.
Someone with more Pentax savvy may want to correct me if I'm all wet on that.
From what I've seen, the default settings go for a slightly more film-like image, which is not as oversharpened as we're used to from digital images. (Which has caused a lot of confusion and undeserved bad press in the net world.) And actually, the K10D does more in-camera processing than the vast majority of DSLRs as it can process RAW files in-camera using settings that you choose (sharpness, saturation, etc).

Anyway, if you want JPGs that are more "typical" of a DSLR, it's just minor adjustments to sharpness and one or two other settings, and there you go. Unfortunately, the damage from Phil's review, where he obsessed on this (which is easily adjustable and honestly, if you're using a K10D you really should be shooting RAW mode anyway), and the camera got stuck with a "bad JPGs" label. I would guess that on their next DSLR, they'll go with a more standard-looking JPGs (like the K100D produces) to try to avoid a repeat of this.
Anyway, back to the point, the included RAW processing software is not too bad. The interface is a little on the clunky side, but for a free bundled program, it's fairly complete and powerful. Lightroom is way better - but it ain't free.
