Sonar's notation is adequate enough for writing drum parts. I do it all the time. It's not a great notation but as long as your not going to in depth, it works.
Otherwise, I write parts out in Finale, save to a midi file and them open the midi file up by right clicking on it and using the "open with" command to open the midi file in Sonar.
To mix each kit piece you'll have to give each piece it's own channel. Under each piece's slider is a number. They will all say 1. Give them their own number. Then create however many audio tracks. Set the input of each audio track to SD3's output.
As far as writing the parts for the drums. I use general midi drum routing. Bass clef, second ledger line below the staff is the kick. Sometimes the
B below the C can be used. You'll have to figure everything out from there. Once you do it enough, you'll know what notes are for what kit piece.