You can use Process | Find/Change to set the lengths of the notes. For example, if you are using 960 ticks per quarters (as set in Preferences), changing all the 480 will make everything eighth notes.
I have not had any problems getting legato passages by using Quantize, but NOTE that Sonar's default has duration set to OFF. You want to check duration in the Quantize dialog box so that all the note lengths will quantize.
You can also do a Select by Filter to select notes that are within a certain duration before you use Quantize.
Not sure if that helps but maybe it will be useful as some point.
Sonar, like most DAWs, is pretty deep, but you should get going pretty quickly given that you have the concepts already and just need to know the mechanics. Sonar started as a MIDI sequencer so I would be surprised if you need anything it doesn't have somewhere.