is ISO, WB, matter when in shooting in RAW?
does such things as saturation, contrast and sharpness matter?
if i shoot in raw, and then only make jpeg in camera with the same settings as my jpeg sharpness, saturation, contrast, will it will be different? (better quality)
It will be processed through the K10D's processor, therefore should be identical to shooting jpeg only. However you do get to do choose the WB, sharpness, contrast, saturation after you have taken the shot rather than before if you have shot jpeg only.
how to get the best quality of images?
Shoot RAW, use good lens, use appropriate camera settings...
does pentax computer software for raw procesing is good? do i need a different one?
Pentax Photo Lab is decent and offer plenty of adjustments. Give it try first, if you don't find it useful in your need then you might as well look at Photoshop, Lightroom, Paintshop Pro etc.
what is most important when converting raw into jpeg?
Probably WB and maybe amount of compression.
if i will not change any settings will it be beter quality, then simple jpeg shot in jpeg mode?
I don't think so. Saving a raw file as jpeg is basically the same as shooting jpeg alone in the camera. They go through the same engine.
If you post process the raw file on a computer, then it might be different. Different software will handle the raw file differently.