A "beginner" isn't going to be able to wrap their brains around all that either the K20D or K-7 have to offer (excepting the K-7's ability to do video). Those are both "advanced" cameras. Why not save a few more pennies up front and get a K2000/Km or a K200D? They're smaller, have simpler learning curves and still produce images large enough to easily print at 16"x20".
"Bodies come and go but Lenses are forever" so it goes. So definitely get the DA*50-135/2.8 if your budget allows - it
is a fantastic lens. But worry about K20D vs K-7 vs K-Q409 after you've got your brain immersed and your feet planted.
That's my $0.02 anyway.