The problem with Importing MIDI files into Sonar is that it will not intepret the notes into Tab correctly. It still takes a fair bit of understanding and experience to correctly map the notes. Take a C note one octave above middle C - it can be played on the 2nd string 1st fret, 3rd string 5th fret, 4th string 10th fret, 5th string 15th fret or 6th string 20th fret. So, for example, there are at least 16 ways to finger the notes C-D (not including octaves). Throw in another note and the possible fingering (Tab) options increase even higher. Properly interpreting the frets is no small matter.
As jb101 and sharke mentioned, check out PowerTab, TablEdit or Guitar Pro, they may suit your needs better. They also allow altering the tempo so you can slow the music down.