I just bought a K10D a week ago. I have graduated from my Panasonic Lumix LMC8 which is also a P&S.
Haven't got to know my K10D well enough to answer your questions...but already I can tell that I'm in a whole new level with the K10D. I'm very happy with the K10D.
I would be careful with that Sunpak flash if I were you, may have too much voltage for a DSLR. Not sure about this..but I'm sure an expert will know and let you know on this thread, if they haven't already.